I struggled to get offered anything over £100. for a nice tidy original 1976 HW35 standard model, complete with it's iron sights, and that was in the more fashionable .177 cal.
The mention of 'light rust' probably puts the OP's gun in the 80-100 bracket IMHO. But you might be lucky and get a bit more.
Seriously good value (probably under-valued) guns...