Not NW either, and kind of an expensive option, but Tri-Mar have Kribs (Pelvicachromis pulcher) in stock for £3.99 each - but you need to add the £10 delivery charge.
However the £10 covers up to 20kg of fish (and water) so if you could get together with some others and put a bigger order together the individual cost per fish will come down. I can highly recommend Tri-Mar, their stock is usually excellent and the owner Monty is a good guy.
or try the japanese koi carp in the east of england they have a huge selection its 1 of the biggest stores in england u shuld give them a ring and ask them they do deliver
I got a pair of Kribs from Trimar recently. I would recommend them although I think there was something wrong with my male when I got him and he died a few days later of unknown causes.