Plants 1 & 2 are some sorts of rhododendron, but as the flowers have finished (those brown dead things at the top of the stems) there isn't really a way of guessing which ones. You could try again for an ID for these two next year when they're in flower.

In picture 3 the central flower is aquilegia. The green things at the top of the stems are unripe seed pods. The low-growing variegated shrubby item surrounding it is a Euonymus, probably Emerald Gaiety. The plant to the left is rather undistinct, but could be a Potentilla. Is that a saucer-shaped flower to the very left of the photo? That would fit with Potentilla.

Rhododendrons MUST have acidic soil,and prefer a dappled shaded site, Aquilegia will take sun or some shade and isn't fussy about soil and Potentilla fruticosa (shrub) likes sun to flower, and isn't fussy. Euonymus fortunei will grow in some shade, or sun. That isn't fussy either.

None of the other plants you've mentioned need acidic soil - they'll all grow on neutral or slightly alkaline soil - apart from most heathers, which do require acidic soil. I say 'most' because there are a few varieties that will grow in neutral to alkaline.

Have you done a soil test to see what your soil is? You can buy a test kit cheaply at a Garden Centre.

By the way, you'll need to decide if you want your Aquilegia to seed itself, which they do, or else cut the stems with seedpods on right back to ground level.

If you're plants are happy then they obviously don't mind the soil. But to give the rhodys a better chance, you could give them a feed of ericaceous fertiliser round the base and mulch with some ericaceous compost.
I agree with Spritzh, get a soil test kit and test areas of your soil. Depending on the size of your garden, you may well find you have pockets of various soil types in your garden.

The rhododendrons are very leggy and look to be planted to close to the fence. I'd definitely give them a feed and consider pruning in the autumn. You could well find that your soil is pretty much neutral so that most things are able to grow in it.

Beattie thank you, I've just done a google search on those plant names and think you have hit the nail on the head. I'll have to get some more pictures of the Rhododendrons next srping when they flower, try to identify the type.

Spritzhenry, no I haven't done a soil pH test yet, I thought I'd give identifying plants a go, but then got very confused when I found several plants that seemed to prefer alkaline soil and a couple that seemed to prefer acidic. I will get a testing kit next time I'm over at a garden centre, do things properly. Nothing round by work unfortunately. Thank you for the information re: shade and sun, that would certainly explain why I don't recall seeing flowers on the potentilla; its in full shade. Should I consider trying to move it or is it better off being left as it is?

2ndhand and Moon Growe the Rhododendrons are planted next to the Lilac, would giving them a feed/mulch for acidic soils hurt the lilac (which I think prefers alkaline soil), the lilac is fully established (was there when we moved in 20 years ago)? Yes they are planted quite close to the fence, we only have quite narrow borders (something which may change if things go well).

Thank you for all the help, its much appreciated.

I'm sure the lilac would be OK in any soil. There were some in our last garden (on acid soil) which were fine.

I think you may be over-emphasising the "alkaline soil" thing. There are acid soil lovers ("ericaceous" plants) which are fussy and don't thrive in alkaline soil, but I don't know of any plants that actually PREFER an alkaline medium. There are some that tolerate quite alkaline soils but grow equally well on neutral or acid soils.

I agree with Beattie I'm not aware of any ornamental plants or shrubs that require an alkaline soil. Lilac 'prefers' a neutral soil and full sun. I think you with have problems with your rhododendrons that close to the fence, the soil looks very dry there, another good reason to mulch them.

If the potentilla is small enough to move, then I would do that - but wait until it's dormant.

I do agree with what's been said about alkaline soil - I wouldn't worry too much about it. It's really only the acid lovers that would suffer and get yellow-y leaves (called 'chlorotic') if they don't grow in the right conditions, and even then, you can water on sequestrene and mulch with ericaceous compost to help them.

Oh ok thanks for that, I've obviously got the wrong end of the stick somewhere along the lines, with the pH thing.

Moon Growe all of the soil in our garden is quite well draining, none of it really seems to hold water. Only time we have ever had issues was when we had all that rain about 2 years ago (when there was massive flooding everywhere), then the bottom of the garden flooded, but since thats mostly concrete garage floor and paving slabs, plus the lowest point on the property its not all that surprising. Even then it drained away quite quickly once the rain stopped. I have plans to dig the majority of the garden (without disturbing existing plants), incorporate some new compost (purchased) to build the soil back up, I'll make a point to get some ericaceous compost as well for round the rhododendrons.

Thank you once again, once I've sorted other photos out I'll most likley be back again asking for other plant IDs. Think I've got most of them pegged now though. I will post some before and after pictures once I get going.

Sam it would have been better to incorporate good humus rich material before you planted to rhododendrons. You need to mulch really well as they like to be in moist - not wet - soil. Also which way does that bed face?

Unfortunately the Rhododendrons were planted by my mum about 2 years ago, pretty sure she doesn't know any more than I do about gardening. My OH has said our house is the only one he has ever been to where the house plants get smaller (I so far have had nothing to do with the house plants). Nothing ever flowers twice in our house lol.

Most of the beds in the garden are fairly bare (since removing weeds and dead things), so I had planned to dig the bare patches, incorporating some new compost, then as per an answer to my previous question, mulch around existing plants. I'll make a point of as you suggest mulching the rhododendrons really well with ericaceous compost. Although I have read a tip elsewhere to carefully dig the mulch in with the soil around the Rhododendrons, which I will try if it’s a good idea.

At a guess I'd say the border faces South West, but I'm really not sure. With the fence there that bed starts getting sun at around 2o’clock ish this time of year. It then stops in full sun until the sun has almost completely set. The only thing giving it any shade at all is the fence behind it.

You suggested pruning the Rhododendrons in the autumn, what do you suggest is the best method (never pruned anything before). I’ve been digging through GoY and found a suggestion to look for the faint rings where one section of growth ended and another began. Apparently there are normally more dormant buds there. Considering how leggy the plants are, I’m not too certain how to go about this though. Using plant 1 as the example, there are about 5 long stems at the top (off the main stem) which bush out a bit at the ends and another at the base of the plant, but nothing in between. I’m not sure how best to prune to encourage it to bush out. Would like to avoid killing it through ignorance (or any other reason) it if at all possible. Any suggestions greatly appreciated.

Sam copy and paste the url below into your web browser, gives far clearer instructions on pruning than I could

http://bit.ly/jnNeGA

Brilliant thanks, I'll have a good dig through site and try to get my head round pruning them. Quite looking forward to it now :D.

Have fun!