Wow I never knew 4-TCs got to Exeter and North Devon. Were they on timetabled services? What years did they run?
I only ever saw them on Portsmouth/Basingstoke - Reading (Sundays only) and Waterloo - Weymouth routes in the 1970s/early 1980s.
The 4TCs plus Class 33/1s regularly got to Exeter St. Davids on scheduled services sometime in the 1970s and 1980s; certainly on Summer Saturdays as extensions of the Waterloo-Salisbury service. Also as replacements for the usual Waterloo-Exeter loco-hauled sets, on occasion.
They definitely got to North Devon (e.g., Torrington, Meeth sidings) on enthusiast specials in the mid-late 1970s, e.g. 16th March 1975: 4TC set 416 + RMB 1872 (one of the two through SR wired ones, S1873 being the other) + 4TC set 413:
33103 (1) London Waterloo - Clapham Junction - Earlsfield - Wimbledon - Surbiton - Woking - Basingstoke - Andover Jn - Salisbury - Gillingham - Yeovil Junction - Honiton - Exeter St Davids - Crediton - Eggesford - Barnstaple - Torrington - Meeth Sidings
33118 (2) Meeth Sidings - Torrington - Barnstaple - Eggesford - Crediton
33103 (1) Crediton - Okehampton - Meldon Quarry
33118 (2) Meldon Quarry - Okehampton - Crediton - Exeter St Davids - (reverse of outward route) - London Waterloo.http://www.sixbellsjunction.co.uk/70s/750316lv.html