"Just had a call, the mac is back at iStore in Crawley and is ready for me to collect it. They say the logic board (motherboard in PC parlance) was replaced under the 6 year consumer warranty thingamo and that is why I was not called because it was free!"
I can't get there to pick it up tomorrow unless my Copaxone is delivered pretty early in the afternoon (1300-1800 slot) so I will have to go Saturday or Monday, unless they are open Sunday and the busses are convenient.
ETA 20150508 Friday: I was awake this morning so I hopped on the bus and am now home again with my mac mini working, plugged in and where I am typing this! I do wish I had asked them to add more