I have just received my copy of the Railway and Canal Historical Society bulletin for Sept-Oct 2015. In it Richard Maund writes about the car sleeper services from Sutton Coldfield
...their post 1958 history (all services were summer-seasonal) was briefly as follows:
Service became tri-weekly from 1961, extended to also serve Inverness from 1961 but reverted to tri-weekly Stirling only from1964, becoming quad-weekly from 1970. Weekly trips added to Newton Abbot (from 1967), St Austell (from 1970) and Inverness (1972 only) Branded as Motorail from 1967. The final season was 1972 and had been tri-weekly to Stirling only (11 Sep), and weekly to Stirling and Inverness (15 Sep), Newton Abbot (16 Sep) and St Austell (17 sep) (these latter were separate services), the dates being last arrivals back at Sutton Coldfield. Hence the last service arrived back on Sunday 17 September 1972.