How about an early flowering one like C macropetala, I have a lovely lilac coloured one flowering from Feb/March depending on the weather. this will extend the flowering interest on the fence. Or a late one.

Then many of the vitcella ones are good doers in the summer. as for colours there are many in the colour palette you are looking for.

Thank you, Seaburngirl, that's given me something to look into.

This is slightly more complicated than it first appears - some clematis need pruning yearly (the viticella, later flowering ones); others aren't pruned at all (early, large flowered varieties such as Nelly Moser). Probably the most important thing is to decide when you want the clematis to be in flower, pick one or two from different groups, ensuring they're far enough apart so that, if you have to prune one and not the other, you can tell them apart where they're growing from at the base for pruning purposes. If you prune your honeysuckle at all, then having a clematis in flower through it when you want to do so will make it difficult.
You do not need to shade the roots from morning sun either - just plant some ground cover in front of the clematis. They prefer a shady cool root run, but this can be provided by ground cover, and its most important in high summer between 11 and 3, not first thing in the morning, so not a problem for you.
Note that the C. macropetala mentioned by Seaburngirl above is a species clematis (as opposed to a large flowered hybrid such as Nelly Moser), doesn't really need pruning unless it gets too large.

Hi Bamboo, thank you for taking the time with your detailed reply. I tend to prune the honeysuckle lightly when it threatens to take over. I was thinking that the clematis would have to be in the same pruning group, 1 or 2, so that pruning would be easier. I'm not too bothered if they both flower at the same time as the contrasting colours will be attractive. Something that flowers late spring and over the summer months would be good, although I'm open to ideas.

Good late spring and summer flowering ones (which don't need pruning really) in the blue/purple range are Lady Northcliffe, Mrs. Cholmondley, The President, William Kennett, Xerxes (sometimes still found under Elsa Spath). Niobe might be worth considering though - it'll probably hold its dark colour better on a north east fence, but in my opinion, doesn't go well with purples. A good white one in the same group is Marie Boisselot (though its also known as Madame le Coultre). You can prune in midwinter if they've got too large, but then you'll sacrifice the earlier, larger flowers - but you'll still get the later, smaller ones.

Bamboo, thank you. I've just had a look at the various ones that you recommend. I love them all, but particularly Mrs Cholmondley, The President and Lady Northcliffe. I've also spotted one called Romance, that is lovely too. Talk about spoilt for choice!! I really need to make up my mind as my local garden centre (The Garden Centre Group, formerly Wyevale) have an offer on plants at the moment. If you order online and collect from your local centre you get the plants for half price. So I really ought to take advantage of this and buy the plants now. I hope that they will survive until April, when I can plant them out. Thank you again for all your advice.

'Guernsey Cream' is another one that prefers a position out of full sun - creamy white flowers in late spring

Thank you, Andrew, I saw that one during my search and it looks lovely, too. Wish I had room for half a dozen!

Hi Pepperty! I was just thinking....Polish Spirit is good in shade and would make a lovely contrast with your honeysuckle. It flowers late in the season and is very floriferous, but it is group 3 so you would cut it down every late winter. A great performer, I love it.

Fujimusume doesn't mind shade and isn't too fussy about being pruned either....lovely one, powder blue.

Viola Venosa Violacea is a great size for a fence and a gorgeous colour and it does really well with many many flowers of medium size..white and violet colours...doesn't mind shade and is another group 3, so easy to deal with.

I grow a lot of Clems in the N. of the UK and have to say I have far more success with the group 3s. They don't get the dreaded wilt, and you don't need to bother about when to prune as it's just a simple chop down to the ground in the late winter (I sometimes do mine in the autumn so I don't have to look at the dead vines through the winter). Just have to be careful with the group 3s that you don't buy one that is going to end up far too big (I've done that many times!) but some of them are really terrific performers. Blue Angel is another stunner!

Karensusan, sorry to disagree, but your statement that late flowering clematis do not suffer from wilt isn't correct - species clematis (montana, tangutica for instance) do not suffer from Wilt, but any and all of the hybrids are susceptible.

sorry bamboo...wasn't meaning to be definitive, just meant in my experience they don't get wilt. I realise they all can get it, you're quite right.

Karensusan, thank you for your suggestions. I had considered the group 3 type and it is appealing to be able to cut the plant right down at the end of the season. However, if the plant has woven itself into the honeysuckle if will be a nightmare to unwind and remove it. I'm still considering which ones to buy so I will have a look at your recommendations.

Another question. I bought a couple of so-called mound forming clematis last year - Bijou and Filigree. One I still have in a pot and the other I put in the border. After the initial flowering the didn't maintain a mound appearance and started trailing. A the moment they are dormant and the leaves have died off. When they come into growth do I prune them to encourage the mound or will that affect the flowering?

According to Taylors they are group 3 so you could prune them hard. My Filigree didn't make it I'm afraid, I may try again, but the Bijou is lovely and it does trail along the ground a bit, but also forms a mound in the summer. I haven't pruned it at all, perhaps I should do so in the late winter. They are such lovely additions to the garden these ground cover clems. Filigree is a beautiful colour too...so soft. :)

I have the Bijou in a tall pot so I will prune it back at the end of March and see what happens. It will look lovely just trailing down the sides of the pot. My Filigree is in a border and I am hoping it will survive the winter. Again I'll prune it in March and hope for the best. I have to say Filigree did seem to be the weaker of the two plants and didn't bloom as well as the Bijou.

Yes, and mine got waterlogged as well :( I will need to try again though, as it is so pretty....I will put it in a better place next time!