[Closed] Replacement car keys - what are the options?

So I've just bought a new, second-hand car but failed to check whether or not the second key they gave me for the vehicle worked or not. And, of course it doesn't. I've replaced the battery but it appears to be goosed.

The main dealer has quoted £320!!! for a replacement. Which feels like (is, blatant) robbery.

Is there an alternative way to get a spare sorted?

Thanks!