Update on my situation. I went the LBS / Madison route. LBS ran diagnostics, which basically said there is a ‘communication error’! LBS sent data file to Madison, 1 week later they asked for the motor to be sent to them. 2 weeks later, after some nagging from LBS, Madison agreed to give me a new motor for half price. Since a motor from them is £ 920 incl VAT, it’s still a lot to pay, but cheaper than one from Germany and it has a full 2 year UK warranty. (Background: my motor had done 4750 km, is 3 years old and had the E010 / W0013 error).
So I would recommend trying Madison first if you’re in the UK. Only thing you might lose is riding time, but you could save some money and have a UK warranty.