To get to Lostwithiel from London, take the M4 westbound towards Bristol. Exit onto the M5 South, then take the A30 towards Bodmin. Turn off at the sign for Lostwithiel and follow the signs to the town.
If you're travelling by train, you can take the Great Western Railway from London Paddington to Lostwithiel station, with a change at Plymouth. From Bristol, you can take the CrossCountry train to Plymouth and then switch to the Great Western Railway for the journey to Lostwithiel.
From nearby towns and cities, such as St Austell, Bodmin or Liskeard, there are regular buses to Lostwithiel. Alternatively, you could rent a car and drive to the town yourself.
If you're already in Cornwall, a scenic route to Lostwithiel would be to take the A390 from Truro, passing through riverside villages of Tresillian and Probus, before arriving in the town.
The closest airport to Lostwithiel is Newquay Airport, which is about 20 miles away. The most direct route is via the A30 and then the A391. Alternatively, you can take the scenic route by going through St Austell and taking the A390. Both routes take approximately 30-40 minutes.