There are many opportunities, especially for those who have bus passes!
09.04 Penryn to Truro 09.18/ 09.27 to Plymouth 10.41/ 10.54 to Gunnislake 11.40 then 12.07 bus to Tavistock for lunch - Tavistock Country Bus 114 at 13.30 on Thursdays to Launceston 14.10; walk down the hill to Launceston Steam Railway for 15.00 train, back about 15.40 and walk uphill for 16.20 bus to Plymouth via Callington 17.39 for tea and then 18.42 to Truro 19.58/ 20.04 to Penryn 20.18.
Cost £6.60 for the train from Penryn to Gunnislake and back from Plymouth with railcard plus £8.75 (concession) for the steam train.
The Launceston Steam Railway runs until 25th September except Saturdays, then October 25th-30th inclusive.
John Thanks John, an idea for when I can find the time.