Thanks Idris. I appreciate your help.
I have tested extensively with my phone too and can confirm it receives calls much more reliably with touch off! I spoke to Albert who reminded me that scientifically the two events may, or may not, be related!! I do not rule out there being something wrong with my phone, albeit new, although it seemed to receive calls well enough yesterday before its number was 'ported.
Nevertheless I thank you for your suggestion of doing the reset as you suggest. I have been holding off on this one as I reckoned it was better to let the carrier make all the suggestions they could first in case the reset confused them or their systems. I reckon you may well be right but intend to cover myself as carefully as I can since, frankly, I don 't care if it is Apple, the carrier, or a bit of each. I will not be left holding the donkey.
One more call to Sky tomorrow to ask why the delay before ringing and the reset settings as you say. Frankly, Apple could stick their phone where the sun don't shine (I "loved" my Windows phone until it got stuck in flight mode but could drag and drop anything, set any tune to a ringtone and play my wma's... if I had bought a better one it would have been always listening but NOT played Skygo or read my texts...). The jury is out!
By the way this takes about 20 secs or more to ring from a landline which includes about 7 secs for the dialling tone. Mobile calls are about 10 secs quicker. I believe this may give an indication as to where the fault(s) lie.
Mike.