All sorted

This is for anyone who has been following my threads and questions. A big thanks to Midland Boiler Care who talked me through various scenarios and eventually suggested that the problem prob lay with the boiler as it shut down with the mid store temp sensor only ever reaching 76 Degrees, cut off being 77 degrees so the boiler pump just kept running 24/7.

I got my pet gas plumber to come out to give the boiler a clean and while there we removed (having checked and renewed virtually every small thing possible over the last 3 months) the heatexchanger thermistor from its dry pocket. Left it out but connected, re-sealed boiler and fired it up, 5 mins of burning later the temp sensor hit 77 Degrees, the call for heat command clicked off and the boiler pump shut down after the prescribed few minutes of run on.

Worth bearing in mind if anyone has simlar issues.

Ideal Classic Slimline boiler fyi.