(I have been trying for some time to find out as much as possible about their route network but have been hitting a brick wall.)
DA picked up INV/LHR from BA around 1983 and operated this route very successfully till the end. G-ATPK, BAC 1-11 srs300 was a regular on this route, later replaced by 500 srs aircraft and finally B737s.
They also operated LGW-MAN-INV & INV-ABZ-LGW for a short period around circa 1990-1991