I finally got around to taking the Fahrrad in for a follow-up service this morning. On Saturdays, the Bicycle Workshop does a first-come, first-served thing - but only the first 10-12 people get lucky. So turning up early is a must.
I got there earlier than I needed to (queues are much shorter in the winter) and was on my own from 07.30 until 07.45, when I was joined by a nice bikey chap with a broken spoke. Turns out he's a Mercian owner and an ex-Thorn owner, so we had lots to talk about!
Ninon (the owner) turned up around 08.15 and assured me that they'd sort out the Fahrrad and sent me on my way. She also said that they'd be getting in the oil change bits for the Rolhoff hubs, which I'll need pretty soon.
Here she is checking in the rest of the bikes for today: