They had a Branch in Park Royal London NW10, I think it was in Chase Rd, and as Heatercathoneshort mentions, fitted at one time (1977?) with a Supermarket Layout, but all those loverly Mullard PL519`s stacked on self service shelves, proved too much of a temptation and a fair bit of hoisting, went on.
I cant imagine any one helped Mr Plod with their enquiries.
The other thing I remember was their Field engineers had very nice MK3 Cortina Estates, a better car than most companies, I had a Viva at the time, working at Granada TV Rental, most had Escorts.
Ken, G6HZG.