The District Nurse (BBC drama, 1984-7 serial, )

Episode 1.10:
District nurse Megan Roberts joins the local brass band and goes on a trip to a brass band competition. Transport is superb preserved 1929 Leyland Lioness/Burlingham DM6228 of Brookes Brothers:
Episode 1.11:
DM6228 appears again, this time in a crash scene which doesn't actually happen until the very end of the episode, when the driver is distracted and swerves to miss a flock of sheep:
Episode 1.12:
The aftermath of the crash: a convincing-looking replica was constructed for the scene, and there are also interior shots:
The replica rear is even better painted than the real thing. Compare the real bus on the left from episode 11 with the overturned replica on the right - on the real one you can see they've covered over 'Rhyl and Prestatyn' (Brooks Brothers' real address) and added the fictional 'Pencwm':
This is my own photograph from the 2007 C(h)obham Rally:
A different episode also included footage shot on a rear entrance bus with a green interior, but I need more information.