I'm back......

and working again! 
I went down to Exeter this morning (far too early for me) and got a "walk in appointment" at the Genius Bar (Apple people will understand) and only had a wait of about half an hour (in Costa!!). the young chap managed to get into the Macbook and ran a full diagnostic and luckily confirmed that there were no hardware problems. So he erased again although that had already been done and reinstalled El Capitan (as I do not want High Sierra) and explained how to restore everything from the Time Machine when I got back home again.
And all this for free...! Whats not to like. Yes I know Apple kit is expensive but to get this sort of service for free on an old Mac is I think excellent and perhaps why initially they cost considerably more than their competitors.
Anyway I'm very pleased with them and will continue to sing their praises.