I don't now if you've tried these, but they're the new generation rechargeables which have a long shelf life without losing too much charge. They're supposed to retain about 85% charge after a year, and that's handy for equipment you don't use regularly, or if you just want a reserve set of batteries that won't go flat all by themselves after a few weeks. There are a few companies offering this type of battery now, but from what I've read the Sanyo eneloop are about the best.
I bought some recently from here...
Component-Shop
They charge £2 for delivery, so 5 sets of 4 come to £34.50 inclusive. Delivery was quick and they included some battery cases and a tester FOC.