Thanks for the feedback guys. Having studied RDR3 meticulously I'm fairly sure I understand all the vagaries of the work less than 3hrs, midnight rule and exceptional circumstances etc. In my case they would rarely apply since I have no business or job in the UK, and my time there is much less than 90 days a year. I also do not fall foul of the Deeming Rule as I perhaps make a maximum of 15-20 trips to the UK a year, mostly for a few days off at a time. Finally, I would only extend my stay for legitimate reasons which would constitute Exceptional Circumstances.
For me the issue is if I can apply the Third Automatic Overseas Test since that determines outright whether I am non-resident or whether I need to apply the Tie-Breaker Rule (which I would fail since I have 3 ties and was resident in at least one of the previous three tax years). As someone who wants to do things right it is vital for me to know the answer to this question.
Avenger, It is heartening to know that the taxmen are 'on our side'. I think I will give them a call when I am next back in Blighty.