I would agree with the above prices. £150-£200.You might get one with some depth of blue and a bit of etching for 150.

Minters are £250-£300 and maybe a bit more for the right gun.

I recently dropped on an early mk1 with most of the etching visible, but I caught it at the right time in a small gun shop when it had just been taken in part exchange, with a couple of other old guns as trade ins. It had not been priced up and I begged it fr £120, which I thought was a good deal.