It's tough to say, as the used market in the UK varies quite a bit to what you'd find here in Canada. I'd check out gumtree or Facebook marketplace and see what you can find, or wait for another user to chime in.
As for whether it's wise to get one, it depends. It's not unwise in the sense that it's a terrible card. It can actually be a pretty decent value if you can get one for a good price and you don't need a GPU for anything other than gaming. So it comes down to what you need it for, and whether you can get anything better for your needs in a similar budget.