Just a quick update, checked the earth points behind the kick panels,cleaned alternator connections and have cleaned the earth strap to the engine. I then noticed that where the negative battery lead gets held in place on the inner wing is also an earth point which was very loose ( previously only cleaned the terminals each end).Remove the lead completely and put the clamp in the vice to tighten it up and put it back on. The heater doesn't make any change in sound now when the lights/back windows demister or anything else is turned on so hopefully will see an improvement at night with the lights.
I have also removed the viscous fan,completely removed the aircon rad,pump etc but left the aircon fans in place and have now connected these up with an adjustable thermostat switch to stop it overheating when stood,it now warms up much quicker and seems more responsive to drive so hopefully will improve mpg too if driven in the same manner as before.