Thanks guys,
I was expecting to be it sort of around those figures. I agree about the boxing, it doesn't matter to most people but some do like it to have original items as you have mentioned. Unfortunately, pellet tin, targets and Instructions have all gone but I probably do have the Allen key still, well at least one of the correct size but I can't guarantee it's the same one! There was a spare air seal with it but I did fit that some years ago.
I've pretty much decided to part with it anyway, I think £90 would be a fair price for it but obviously only I know of its condition, in my opinion it is worth this amount.