For those going on Friday 26th, as follows.

Exeter St Davids
Departs 09.25, Totnes arrives 10.01

Totnes Riverside diesel departs 10.30 (South Devon Railway)
Staverton arrives 10.45

Bar opens 11.00

Homeward
Staverton departs 17.00, 17.40
Totnes Riverside arrives 17.15, 17.55
Totnes mainline departs 17.49, 18.19
Exeter arrives 18.21, 19.00

For SATURDAY - times are slightly later by a few minutes

I believe it is possible to get there by bus no. 7

Info from Timothy the Transport Officer