(Sorry to prove you wrong Richard, but I've got the cross-sections book your mention above and that's not quite right.)
According to Classic Thunderbirds: Secret Files (The Inside Story of International Rescue (Chris Bentley, Stephen Cole and Graham Beathman) the power sources are as follows:
- Thunderbirds 1-4: 'Atomic fusion reactor(s)'
- Thunderbird 5: 'Atomic batteries'
- The Mole:
- The Mole (Drilling part): 'Nuclear-fusion powered electric motors'
- Trolley: '1,000 bhp high-compression dual-turbine engine'
- FAB 1 (engine): 'Modified Rolls-Royce gas turbine [and Vortex] aquajet for water travel'
- FAB 2 (the yacht seen on 'The Man from MI-5'): '2 gas turbines driving magneto-hydro-dynamic aquajets'
And just if you're interested:
- Sun Probe used 'toxeriene' as fuel for the rockets and had an ion drive
- From Thunderbirds (2004) all craft used a 'Hackenbacker series 3000 fusion reactor' except Thunderbird 4 which used a 'hydrogen fuel cell power plant' (FAB 1 used a miniature version of the reactor)
Although I can't see any official endorsement on the book itself by Mr Anderson (RIP), it is published by Carlton, so that should add to its canon status (as a major Thunderbirds fan myself I rely on it regularly in Thunderbirds matters).
And regarding my above comment that annual I was referring to was the official 1992 Thunderbirds Annual (is this the one you mentioned above?) It also refers to the craft having atomic generators for power source in the short story Missile Alert and the thing I was thinking of was silver nitroglobe, used to cool the atomic generators.