I used maidenhead for my first lot of cories,and they sold so called C.Julli for £5 each or 3 for £12,(later id has C.trilineatus.)
Then i bought some peppers 3 for £6,that went back has i wasn't happy with them.
I've seen a lot of corys on my travels varying between £1.50-£30,usually when i see them cheap there's normally a dead fish in the tank also,so i don't think its worth the stress on buying them!
Lately i've used Cadburys garden centre,their price for leopard and skunks which i recently bought were £4.95 each.
maidenhead are expensive,but to warant prices like that is unbelievable!!