So I took the offending i-mac back to John Lewis, and after three hours of negotiating like Henry Kissinger, they did me an upgrade to a nicer 27inch bigger 5k new i-mac. This was finally an acceptable solution. It’s only a bit of a shame it was quite such hard work to get there. Morals of the story? – Great service is more a slogan than a reality even in places where once it was true ( a small sign of the times); Stuff on earth gets corrupted by moth and rust, the Bible tells you so, so expect it; It is often true (Grace aside) that you don’t ask you don’t get, so ask God and ask the people, and keep on asking, persistence works well with patience.