I second the nook simple touch glowlight, got mine from sainsbury's £49.99.
I have a sony prs 505, with lot's of epubs and other stuff including kindle content all mixed in calibre.
I too wanted sd card storage and this does it well up to 32gb.I sent back (not Joking) 3 kindle paperwhite's as all had issues,which was really irritating at £109 a pop,yet the nook at half the price has been perfect. The kindle has a better selection of books, but with the nook I can sideload any epub onto the sd card. Library books as well. The light can be switched off completely if you wish, as can wi-fi,it also has manual page turn buttons. Hope this helps in your choice.
