Rifle Scopes Bushnell Elite

I am thinking of upgrading my rifle scope and was wondering if anyone knows roughly how much my Bushnell Elite 4200 4-16x40 Sidefocus is worth in the UK?
It is nearly one year old and has been used for about 300 shots on my rifle.
It comes with its original packaging and paperwork and is in immaculate condition with only slight marks where the rings have clamped it.
I paid £500 for it when new and it has proved to be an excellent and accurate scope at upto 600 yards.
Any ideas would be much appreciated.

Cheers
Midge.