Is the fan working correctly/going up in speed on higher temps? You can check with speedfan or GPU-Z, most likely.
Yes the fan speeds up as the temps rise and throttles back when they begin to drop. I regularly clean my PCM and components with an aerosol spray duster which blows out any dust. A custom profile in afterburner burner which was mentioned above might be the way forward. Thanks for your suggestions. This card is ageing but it will still max out any game I've got so will stick with it for now.