they appeared on passenger workings, maybee specials..
quote from Taunton Trains
'''The 28th May 1984 saw another rare Class 40 foray into the South West, L.L.S./ T & N Railtours operated 'The Devonian' utilizing a pair of Class 40's to head South. Running as the 1Z26 throughout, the tour operated as follows:
40057+40135 operated the tour from Preston - Exeter St Davids. At Exeter the train was split, The Class 40's took 4 coaches on to Paignton. The remainder of the train then took in the delights of Meldon Quarry and the Heathfield Branch before ending up back in Paignton. 31259 & 31180 were used for this leg.
Once back in Paignton the train was reformed and the two Class 40's worked the train back to Bristol Temple Meads. At Bristol the Class 40's were removed (as 057 had failed) and 47199 was utilized for the trip to Crewe, before 40177 was added for the remaining distance to Preston.
this from the website"
http://www.tauntontrains.co.uk/MEMORIES-RAILTOURS.htm
another page there says
"You may also be interested to know that around that time class 40's also appeared on odd occasions - I remember the first one well having seen it from a distance heading south and later enquiries leading to its identity - which escapes me just now! I think it was also heading a special goods working to Taunton. On odd occasions after that (still quite rare though!) 40's appeared on trains to Bridgwater Cellophane works among others and I remember one heading North through Highbridge on 16 ton coal hoppers which had apparently come from Exeter Riverside one lunchtime.