(BBC comedy series, 1975)

Ostensibly set in Oxford, and features two Oxford-South Midland double-deckers in the opening credits. First seen is this 1975 lowheight Bristol VRTSL2/Eastern Coachworks, crossing Magdalen Bridge, blurred but I believe it's 442 (JWL995N):

It's followed by a Daimler Fleetline/Alexander, one of the lowheight batch TFC397-416K new in 1971: