Do you mean the halogen ones that look like a big glass bowl with a light and a fan in the top (well, they don't just look like that, they are like that), or do you mean the box shaped ones that are just like a mini conventional oven ?
If the latter - don't know.
If the former, I have one (JML do them but mine was from somewhere else) and they are really good. There was a thread a little while back and I think if you search for halogen ovens you should find it.
I know that you can get them in TJ Hughes now, but other than that they are only online or from the TV or those magazines that come with the Sunday papers.
They are not perfect (what is), but if you live alone - or are a small family (mine is smaller than the JML one so that is why I said live alone), or are limited for space they are great - cheap and easy to use, easy to clean and cook really quickly. I use mine loads. My Dad was so impressed that he bought himself one.