Look it over carefully. If it looks good on the outside there's a better chance it's okay on the inside. Check the bore carefully. Do they have a return policy if there are issues? Can you shoot it before you buy? Can you deal with the imperfections that come with a used firearm?
IMHO, I would choose a nice used 10/22 over a new one anytime, and not just because I'm cheap. :lol:
Hi and welcome to the forum! Are you in England? I didn't think you could own guns over there anymore. Those prices seem real steep by US standards but I guess it is a seller's market. I suppose someone some where has worn out a 10/22 but I've never seen it. Any scratches on the stainless ones can be buffed out, just remember the receiver isn't stainless. As long as it hasn't been run over by a steam roller you can replace or upgrade almost every part on it, but the stock ones shoot just fine. Get the used one, you'll get the urge to tinker with it as soon as you see some of the ones people have built on this and other forums.
Good Luck,
Cape Cod Terry