All depends if you can get it off without cutting.
If you cut it i would say it would be worth up to £30.
If uncut, a bit more.
Sam!
If it was a replacement from Renault fitted 3 months ago then it would be in 2 pieces anyway (even though the originals were in 1 piece). If you are happy for me to arrange a courier to pick it up and if it is a Renault supplied cat back (£501 is very cheap for a Renault exhaust) on the basis that it will be in good nick being only 3 months old I will give you £120 for it. Could you email me any pics to confirm? I'll pm you my email address.