There are loads for under that price, any worth buying though? That is the question.
Do you currently have an Android phone? Which one?
The only Tablets worth buying at the moment, in my opinion, is the Advent Vega and the Archos 101 (or 70 - a 7" version). There are a load of other tablets (or e-books out there) but few will support any future Android updates (if at all, especially the chinese copies).
There is of course, if your feeling brave, the xda forums, but how much support these tablets will get on there? You maybe on your own rooting and flashing. And if you don't know what those mean, then you may get lost pretty quickly.
But I would say, wait till after Xmas (unless you are absolutely desperate). In the new year, more details will come out for better tablets (when Android officially supports them), people like ACER, HTC, and a new Samsung will no doubt be out.
As for getting hold of an Archos 101/70 or a Advent Vega? Just keep checking Currys/Dixons/PC World, and Archos.com.
If you want a basic tablet for some browsing, emailing, and maybe e-book reading, then you can pick up something decent for that price. But if you want a big version of your phone, then it is probably worth waiting.