Here is Crocus's website, they sell all kinds of garden plants.

And here is the Gardener's World page which includes the link to Crocus which will automatically give you a 20% discount at the checkout.

I recently bought seven plants from there, and would recommend them with a word of caution:

Ordering was smooth and easy, delivery was quick, the plants arrived 2 days later, and they sent the right plants which were reasonably well protected with cardboard and cling film and tape, and plants were well watered.

So now, the word of caution: some of the plants were sold in 2 Litre pots, and priced accordingly, but although they were technically in 2L pots, a few of them had quite clearly only just been potted up from much smaller pots, so they were not well-established 2L rootballs, and the pot was mostly filled with compost, while the plants were really only half-litre rootball size ... and when I tipped my 2L paeony out for planting, almost all the compost fell off and I was left holding a small piece of bare root ... luckily it has survived and started to grow now.

Most of the plants were in excellent condition, although 1 out of the 7 was in poor condition and I wouldn't have bought it from a garden centre if I had seen it looking so dismal, but hopefully it will be ok now.

Buying plants from large national suppliers is always a bit risky, but all in all, I am planning to order from Crocus again in the autumn because they have some lovely plants which I haven't seen locally.