The following Travel links will help you get to Cornwall
Rail / Train Travel from London Paddington (via Reading for Heathrow) is through
Trains from other parts of the country are through
Coach Travel within the UK can be booked through
National Express who run a good service to Cornwall with a large number of destinations.
Road Travel routes can be planned at
Bus Services within Cornwall are mostly operated by
Air Travel
The Local Airports are now Newquay and Exeter(in Devon), but if your nearest airport has no flights to either of those, you can fly into London and catch the train.