An update. Well some 3 years later and this noise still keeps coming back, it only happens once the engine is hot and only when welly is applied. Now as i wrote previously with an oil and filter change this noise dissapears completly as it has again with the recent oil and filter change. My plan from now going forward is to carry out oil and filter changes at 3000 mile intervals.
Just got to sort out the rear end clunking and knocking now thats more of a worry. Mot next week...