There are UK eReader users; but you need to purchase the devices online rather than in high street shops.
I don't read PDFs myself but the Iliad seems to be generally regarded as the best option for that format.
If you haven't already discovered it, the comparison matrix is a good starting point:
https://wiki.mobileread.com/wiki/E-book_Reader_Matrix
And there are lots of other threads from people in the same quandary previously
Good luck - hope you find one to suit
