Helliwells were also at Castle Bromwich and involved with Spifire preperation, I had the privellege of meeting their Chief Engineer once.
Eric Bott who operated the maintenace at BHX till around 1980 (Eric Bott Aviation Services) also worked for Helliwells.
Walsall was regularly used by TI's Dove ans I seem to rember there were a few light aircraft flying out of there in the 60s.
Butler Lamps were owned by Lucas,