DI.
You're today's winner nine-fiver, it was indeed the DI!
Just got back home. The mechanic that came from the motoring club seemed very competent. He very quickly decided it might be the DI, but removed it & smelt it and thought it was OK. Tried a couple of other sensible things, including checking for fault codes. Luckily, despite our move to Austria and all the upheaval it involved, I kept a spare DI cartridge at home - not new, it's about 4 years old. So he gave me a lift home to collect it, connected it up and instant life! Quite a relief as I need to leave home at 8:15 tomorrow morning for a 120 mile round trip to Linz airport.
So, since I'm now running a four-year old DI in the car, my mission today will be to buy a new replacement and keep this one as a spare again.
Thanks for taking the time to reply everyone. I did suggest the CPS to him (no idea what the German is for that but he understood!). Perhaps I should get a spare one of those just in case, that's 10 years old!