Not really North London (in fact, you could argue it's East London), but I get all the work on my bike done at Essential Rubber (just off Kingsland Road, near the fire station):
27-29 Downham Road
London
N1 5AA
020 7241 0055
They offer a ride-in service for tryes, MOTs, repairs, and all without having to book in first. Absolutely top guys and possibly the only repair place (motorbike or car) that I have never heard anyone complain about* (and considering I work in the motorbike industry, I get to hear a lot

).
I think they are open late on a Wednesday, and I know they can come out a collect your bike for you.
HTH
Jo
* To give an example, a customer of mine (I sell motorbike clothing, but don't deal with parts/repairs etc) was having an on-going electrical problem with her bike that another repair centre had failed to solve. I gave her Essential Rubber's number. She came back a week later to tell me what had happened...ER sent out a van, picked up her bike, found the fault, fixed it, and returned it to her (with her paying over the phone). Altogether they had the bike for three days and they phoned her everyday to give her an update!
P.s. I don't have any business connection with this company, I just trust them to do the job well and not overcharge me nor do work that doesn't need doing, so I like to pass on the recommendation when I can
