You could wait for Amazon's Kindle Fire, that promises to be decent and will supposedly be under £150.
Because the tablet device is so dependant on the feel of both the physical thing and the user interface, you need to go and try some.
I found that a big HMV in Central London (Toccadero) had a selection of tablets to try, including the Archos, Samsung and a few others I can't remember, alongside the obvious iPad.
Play.com are having a sale, here's an
Archos for £230.