I never sell to pet stores. No clue what the internet community is like on your side of the pond, but buying and selling fish online and shipping or receiving them is a becoming more common now. Fish that aren't available in stores, and with little or no risk of contaminating your tank with disease or parasites if you deal with people breeding/raising the stock at home, make it quite attractive. Prices are often lower as well, which offsets the shipping cost. Aquarium forums are good places to find other hobbyists who have bred fish and want to move them along. There are also less specific online classified ads like Craiglist available.