The engine warning light came on - knowing the fault could be quite trivial, I checked the lights and sure enough I found a blown brake-light bulb.

I changed the bulb (cost £1) but the (expletive deleted) warning light stayed on. Rang the indy VW specialist who service the car, they said 'that happens sometimes' and that they'd need to plug in the diagnostics computer to clear it, which they did for £22+VAT.

Interestingly they couldn't see a fault-code for the failed light, only some other minor transient faults, but anyway......this blown bulb cost me over £27 in the end. How can it be right that the ECU retains the warning for a blown bulb permanently and doesn't clear it when I replace the bulb? Obviously I had to get the fault cleared as there's just the one warning light on this car, for everything from trivia to impending disaster. So a terrible waste of my precious time and hard-earned money when on a normal old-fashioned car the cost would have been....£1.