Do you want to buy shrubs or perennials ?
I wrote a blog on some good online perennial suppliers and, there are a number of online companies selling shrubs too - have a 'search' for garden centres online ... i've done it a few times and there are quite a few to choose from.

Plantsbypost are very good also Dobbies. . T&M dont get me started. been rowing with them!!! and dont use Garden supply direct I have been waiting over 3 weeks for my order, no emails nothing!!! Never again

Jersey plants direct good quality plants and you get cash back if you order through cash back kings .

I got my begonia plug plants last week and they were rotten very wet plants with very bad root system.

like most of these companies there are good and bad for them all. I have had several good plants from van meuwen, my only gripe is the lack of good naming on the plants. eg I bought some lovely healthy leucanthemums and when I asked which variety they were they said the were unable to tell me.
Phlox were just named by colour. I did explain why I wanted to know but they were unmoved.

I have had mixed quality from Parkers and T&M.
Still waiting for a replacement aconite from Garden Express but they are still talking to me about it.
I must say Bob Brown's nursery Cotswold garden flowers is excellent, though not cheap.

I have been using eBay for the last two years or so they is absolutely loads of sellers from all over the world to choose from you can buy common annuals to ultra rare stuff that are not usually available in nurseries/garden centres. My latest buys include some very rare flowering size South African amaryllis bulbs, Calla lily Hercules, and Ixia viridiflora flowering size bulbs from Australia (they took 4 day to get here).Just look at the sellers feedback anything above 98% should be OK.

Just had replacement begonias from garden direct but have to say these are not much better.

I know its beena long cold winter bu tcompainies should send out quality plants.

I have ordered cyclamen seeds from ebay and been happy but last year one was cyclamen corms and there were only 4 expensive but thsi was what I wanted for my woodlane area.

They are in aseed tray but not looking like cylamen so waiting till they bloom and shallpost a photo.

Dt Browns is a fairly good garden website and fairly reasonably priced.Ive not had a probem with DT Browns not like i have had with thompson and morgan.

Ive ordered shrubs and trees of browns and had no prob's

I'd seen on the van meuwen website a deal for 3 x clematis - winter beauty so i was thinking of ordering them when i get back off my holidays. I also want to get 3 more plants for the garden but not sure what yet. All i know is i want them to be perennials, grow to no higher than 60cm and looks great among my bleeding heart plants. I was thinking possibly purple or white.
I shall definitely spend my time looking at all the websites everyone has suggested, thanks again