Cheers matey, one of the best changes I have done to my 5
I don't think the 19 rear back bench would fit the 5 but the lower section might, without seeing the frames for the 19 I am really unable to tell if they are the same as the clio valver jobbies.
If I was you try and get some clio valver leather seats they come up on the clio 16v forum now and again. In fact I know a bloke in surrey whom has a set of grey leathers ones like mine but is missing one of the front subframes. He was after £120.00 for them but they are in good condition.