I wouldn't recommend the Elonex; Sony is much better. But you also have to consider the Kindle now too, which will cost a total of about 215 pounds, and offers the most books--but is limited DRM-wise.
The Sony is 229 but you can't purchase ebooks from Sony's online store in the UK; you buy from online sellers like Books on Board, Waterstone's, Borders, etc.
I started a poll question
here regarding new UK ereaders, and the PRS-600 seems to be the favorite.
And no, you can't lend DRM-ed (purchased) ebooks, although Barnes and Noble is trying to make that happen with their new reader (pending).
Click on my signature to read more about all these ebook readers. I have just about every UK model described on my website . . .