That was Jah Tubby Sound in Broadway Market E.8, been gone a long, long time, I used to go there along with Pete Lawson to get stuff cut, he may well have sold to Brum, most of his customers were from there.
Music House at that time (mid to late 80's) was located in Finsbury Park, just upfrom the station, it moved to Holloway (handy for Keb) in the 90's.