My thanks to Nick for taking a call out-of-the-blue for which there was no 'job' in it for him - so giving me his time for no reward. Having read with great interest his article "https://www.hellistreeconsultants.co.uk/page/why-topping-trees-is-a-bad-idea/133/", I had some follow up questions and his advice has been very helpful.
I particularly like Nick's approach to tree maintenance which takes into account the value of a tree to one's property value too.