If they're free, they are almost certainly pirate.
Have you tried Inkmesh ? It's a book search engine, specify ebook, and it will show a number of places to get it - if it's buyable in ebook that is.
Some will be US, but I've bought from some of the stores OK, but it will show sterling if it's out there.
I expect there are similar engines, but Inkmesh is neat.