How do you know those eBay listings are fakes, though? Most listings I see are genuine, even if some listings are a bit deceptive because they're selling a World Tournament version of an in-demand card (which is official TPCi manufactured merchandise, just not considered to be the actual card itself, and is not play-legal in tournaments because they're considered "marked").
It should be worth noting that you can minimize your chances of having the cards turn out to be fakes (which are very low chances to begin with if you actually know what you're looking for) by only buying from top-rated sellers.
Though I'm not surprised on the prices being high for someone in the UK, since most listings for Pokemon cards in English are posted by sellers based in the US.
Being from the US, I do not know of any UK singles sellers. You might try your local hobby shop, especially if there's a Pokemon league based there, but chances are low that they will actually deal in Pokemon singles.
Amazon is just as risky a venture as eBay is for buying singles.
Otherwise you could try US-based card retailers like PokeOrder, Troll and Toad, and Collector's Cache.