Posted: 01/10/2012 at 19:02
As you have a clay, wet (I assume with the summer we've just had), soil I'd try growing them either in large pots (as Geoff suggests) or in raised beds. Raspberries don't really need a lot of organic matter mixed in, but they absolutely hate their roots sitting in a wet trench.
Also be careful not to plant the stems too deep, it's not necessary to plant them below the soil level you bought them with, and dig the trench a foot to 18 inches wide so the roots have plenty of room to spread out.
If you want to try something which isn't quite as fussy then you could plant blackberries which will tolerate a wetter soil to a certain extent.