I've had a couple of these and for a good one £300 to £350 tops is fair. The issue with these is that there can be problems with the crown and stem, it can be weak and a bit wobbly. The watch was head only with fixed bars and a NATO strap.
There is strong demand for this watch and if no issues should sell in a heartbeat. Trade is more tricky as it requires two like minded people. Might be better to get the cash and then look for what you want.