where are you based? If you can get to Crawley, it's worth going to the Evans Cycles in Gatwick because it has the big warehouse there and you can get to see all the different permutations of padded shorts!
Thanks all - the one I've found that I am aiming for is OW - it's called the Huntsman. I reckon I can take people on the bike, but I certainly can't in the run. Basically I just want to give one a go to see what all the fuss is about - I don't need to buy any kit because I own a pair of trainers, I am a kayaker so have wetsuits with loads of movement in the shoulder and I obviously have a bike. What can possibly go wrong?! Also I need to do some different types of exercise to shift a bit of weight - I'm podgier round the middle than I'd like to be and cycling miles on end has stopped having an effect.