So I ended up getting iRex Technologies iLiad e-book reader. I have been using it for about a month now, and I absolutely love it! I usually switch it on so I can read it on the way to Canary Wharf (currently doing a contract out there), and leave it on the whole day. It's like having an iPod - but for books. I've installed an 8GB SD card, and I've got lots of books and maths and computing papers loaded.