Yep, checked ebay UK site and there are a few listed. He can use mine for a while and if it works for him I will get a Sony 500 for him. (I don't want to spend a lot of money on it anyway).
He is actually a good reader, but continually loses his place and skips words. After 3 -4 pages it gets worse and he starts rubbing his eyes. The overlays make reading more comfortable. The glossy reflective surface of computer screens make it worse which is why I'm keen to try him on an ebook reader.
He uses a computer in school as well for writing and uses software called co:writer to help with spelling. Computers are great tools!!
We'll let you know how we get on. Thanks for your help everyone.