Don't think you are correct. The red brick building was built as the Sutton Labour party headquarters and was originally a single story office but never a garage. It was expanded to three stories in the 60s/70s. The Plymouth depot was off Salisbury Road to the rear of the same block. I used to walk past it everyday on the way to school. It was referred to as Drake Carriers garage who may have been the original owners. While waiting for the no 3 bus, I used to note the movements of Scarabs, Highwayman, D Series tractor units and BMC parcel vans that used to be serviced there. The garage was demolished years ago and was replaced by a housing development called Drake Court.