Episode 3.06:
A shame we done't see more: seen in the background of the car park at Newmarket Racecourse are two double deck buses. One is an Eastern Counties Bristol VRTSL or VRTSL2 with ECW body, the other an Ipswich Borough Transport Leyland Atlantean/Roe!
Episode 4.04:
A scene set in London, and an AEC Routemaster on route 8 passes a taxi and an Underground station - except this isn't London at all. The minibus in the background is an Eastern Counties Ford Transit/Dormobile, a so-called 'Snoopy':
As the RM moves on, the London Transport roundel proves to have been fitted to an Eastern Counties bus station building. Nigel Utting comments "That's Surrey Street passing the bottom of Norwich bus station which has since been completely redeveloped. The minibus would be one of D779 NUD or E851-6 PEX."