I go to Ross and have been doing so for many years for my units.
The thing with Ross is that you must go in with the unit fully attached and ready to go.
I dont think he is a real expert in attachents and things like that and also dont expect him to cut down any stock units to fit you either.
He is simply is great hairdresser and has a great deal of experience in cutting units in, all you have to do is tell him what you want.
He takes his time and is very thorough.
If you are after a hairdresser who knows how to cut units in and who is a genuinely good bloke, then you wont be dissapointed.
Thats my experience anyway.