Hi, Ray:
I live in the US, not the UK, so we're at opposite ends of The Pond! Around here, the place to look for mandos (as well as other fine instruments) is a shop called Mandolin Brothers in Staten Island, New York. I went there in May but saw no Holoubeks.

I did an internet search for TAMCO (The Acoustic Music Company) in Brighton, and came across some pictures at this guy's site -- looks like the shop is set up similarly to our "Mandolin Bros." Crowded rooms with instruments on the walls and all over the place. Must be a great place to spend a day! (...and a lot of money, I'm guessing...)

Sharon