Depends on calibre, condition and sometimes how nice the Walnut is (not that that should effect the value but it helps to sell it).

All depends on if it's a mk1 or 2 S (could even be a mk3 but they had Deluxe Beech stocks), does it still have the open sights and any original bits it came with (box etc)

I've seen them go between £150 to 325 but the average seems to be £275ish.

Pete