I live in North London, so they are relatively local to me, at least I can drive there quite easily. I used to use them to set up and mod my basses but they messed up with one bass and instead of apologising and getting it sorted, I got excuses as to why something I requested wasn't done. This was an employee mind, not Martin. Since then I decided to learn how to set up and mod my basses myself.
I have bought from them before and I would buy from them again if they had something I liked, just be aware that, as per the OP's post, occasionally communication between them and you will be poor and you might have to chase.