My LBS, Comptons in Catford, is still going. I think their main points are being a Brompton dealer and offering good workshop services. They're right next door to a big
Halfords so competing on bread and butter BSOs must be hard.
I use them a lot for jobs that are too difficult/ fiddly / boring / important to do myself. Experience has also taught me is that not only do they do things quicker than me they actually do things right.