It is very easy to get to Torquay from London. I explain some possibilities:
1- BY PLANE: The nearest international airpots are Exter and Bristol. Easyjet fly to Barcelona from Bristol. A taxi transfer Bristol – Torquay is available.
There are others airports:
a. Heathrow: there is a direct coach to Torquay.
b. Gatwick, Stansted and Luton: you will need to take a connecting bus to Heathrow or a train to Central London.
2- BY TRAIN: International Trains arrive at London Waterloo. From here, take bus number 211 to Victoria coach Station (Not Victoria train station!)
3- BY COACH: from Victoria Coach Station in London
Timetible:
Depart Victoria Depart Heathrow Arrive in Torquay
07.45 08.40 13.30
10.30 11.25 16.05
12.30 13.20 17.40
14.30 15.20 19.50
16.30 17.25 21.35
18.30 19.20 23.30
23.00 23.40 04.55
4- BY CAR: there is a ferry to cross from Calais to Dover.
5- BY BOAT: from Santander (Spain)
I think the best, easiest, cheapest and shortest wat to arrive in Torquay is by plane London (Heathrow airport) and afterwards to take a coach to Torquay.