Yes - if they're from Taylor's they'll be fine. It was hard to see from the photos Why do you put slabs over the clematis @WillDB?
...I use compost around the base formed into a 'berm', like a mound up the lower stems about 4 or 5 inches which will subside and settle over time... it protects the emerging shoots from slugs I have found, and encourages rapid growth....nothing else..''like nearly all climbing plants which we grow, all clematises in nature hoist themselves up through shrubs and into trees, while their roots are perforce in shade, this should be borne in mind when planting, though every now and again a plant will be seen thriving in hot sunshine..''G.S. Thomas.. one of the greatest plantsmen we've had in this country..To assert that a well established practice is a myth, one should provide some degree of evidence... I don't always provide shade myself though but I get better results when I do..