Oh man, both The Enemy Within and Dog Eat Dog certainly fall within the upper quartile of quality UK gameshows, although probably nearer the bottom end.
First series of DED is OK, but it doesn't really hit it's stride until it's second and third series, which are really splendid. Series four tends to put too much emphasis on contestant bitching and the games seem to be laughably easy.
The Enemy Within is a lot of fun, and Lythgoe is a very good host of it.