Carole, most designs that are charted for DMC perles should transfer, although they may look a little difference because the "balance" between the thicker and thinner thread will be different. Anything with speciality threads you would have to experiment a little to find the required thicknesses.
Another thing to bear in mind is that if your afghan has lines woven into it (as on my picture), you will have to make sure that none of the cut areas are on those lines as I don't think that would work.
If you like 18ct but it doesn't necessarily have to be an afghan, you could use Zweigart's Davosa fabric; I've used that and it is really nice to use (or if you are willing to go to 20ct, Bellana comes in sparkly varieties too

). Whatever fabric you use, make sure the weave is not too loose; it's a bit difficult to define what exactly is "too loose", but basically the Kloster blocks should sit quite snugly on the fabric without moving about too much.
If you like the afghans with 5" squares on them, like the one I've used here, then all the Round Dozen designs would be just the right size for that, and of course the two Afghan Squares I'm doing at the moment are, too.
Reference book -- I think Mary Hickmott's Easing Into Hardanger is probably the clearest introduction, and quite affordable (£4.49 from Sew & So). And if there are things you'd like to discuss or ask about, just drop me a line

.