Was in Woolworths today and they are having a good clearance on their plants and shrubs. Clematis £1.50, Camelia £1.50 etc. Plenty variety and only very few are possibly dead. That was the former Big W at Milton Road Edinburgh. Can't say if other smaller stores will stock plants or not, but I believe there are quite a few warehouse style Woolworths around the country. They also have seeds instore for all different plants and veg for 60p [down from £1.99 etc] which are good until 2009/10/11.
The average price of a clematis is around £7/£8