Having recently packed up my property for moving home I have come across my old air rifle and wondered, in the first instance, what value it may hold, and secondly where might I be able to sell it?

It works fine, and the little research I have undertaken leads me to believe it may be of the 'Target' version due to the hexagonal block at the muzzle. It has a right hand lever with dual dial rear mounted scope.
I have a variety of photographs available, but other than this I do not really know what direction to head. It is of little use to me, but obviously I wanted to ensure that I gained a fair price for what is a classic air rifle, and ensure that its sale was above board and responsible.

Any help with direction regarding either of these queries?