There is no direct train service between Heathrow and Truro. Your best (and cheapest) option would be to take a bus to Reading (pronounced redding) and then get a train from there directly to Truro. The journey takes about 5 hours.
The adult, one-way fare from Heathrow Airport to Truro, Cornwall via London Paddington on the train is about £30.
By train to Truro and then a bus
The driving distance is about 284 road miles.
City of Truro
The distance from Truro, Nova Scotia to Antigonish, Nova Scotia is 65.34 miles or 105.16 kilometers.
174 to Truro
532 road miles form Truro, MA to Fredericton, NB
There are 200 kilometers from Truro to Canning. === ===
About 820 miles.
About 6 hours
4,000km
Truro to Vancouver is 3545 miles.