raymond evison isthe best...i have met him at chelsea a few times and he is very friendly and he sells his huge clematis some are several feet tall for a fiver if single an £8-£10 if doubles.
i spoke to him about the tsv he did the year when qvc customers got "rebbecca" before everyone even chelsea. very pleasant and very humble.
bought a smaller more free flowering one i believe it is cezanne...
if you notice he brings in all the plants fully grown for the tsv's and does not do "mock ups" like some of the other suppliers.
i and my mum are his number one fans as all his glorious plants grow very well.
if you get a little stuck on planting them up just post a question or go on his website and ask a question.....happy clematis growing...