Don't even consider an 8400.

Card with numbers like 9500, 8600, 8400 are just trying to fool people into thinking they are just toned down versions of 8800s and 9800s. They are not. Don't buy them. Look at the ammount of memory on it, it's just meant to make people go, "Oooh, that card has as much memory as a GTX280, therefore it must be good!". 1GB on a card like that is a total waste.

Get a second hand 8800GT if you can, or a new one or even stretch to a 4850 and you won't regret it.

Your last comment, "That brought it down to £390", is confusing me. Yes, if you get something inferior, it's going to bring the price down. It's like saying, "If I don't buy any food I can save £100 a week!", uh yeah, but you won't have any food....

If you want, I can spec you a good PC to fit in your budget. Just don't go off buying 8400s or 9500s lol xD.