Report:
Very knowledgeable (and nice) mechanic from Perranwell came round last night and managed to get it started. Seems it was not the ecu but a problem with a camshaft sensor. Laptop diagnostics flagged up "camshaft out of phase". We removed the two cam position sensors (simple hall effect triggers)at the back of the rocker covers, wiped them with a rag and re-installed them and re-connected the electrical connectors. Bingo, it started and ran fine. I can only guess one of the electrical connector pins was not making contact. The car was running perfectly when I last used it after an 800-miles trip to the Loire in early September but I had not started it since then due hospital/knee replacement op'. Whether leaving it for six weeks (on trickle charger) could have caused
the "out of phase" problem I've no idea. Maybe I'll carry a spare cam sensor in future.
That sounds like great service from Perranwell. Well done to them. Hope you get out again to enjoy it. Perhaps Perranwell could have replaced your knee for you?