Factual error: As the Hood approaches central London in Thunderbird 2, they fly through Tower Bridge and over HMS Belfast, approaching from the East. However the onboard display in Thunderbird 1 shows TB2 approaching from the West, somewhere over Hammersmith.
Factual error: About 2/3 of the way through the film, the Hood uses an electro-magnetic pulse device to disable the alarms in the Bank of England: the lights in the vault remain completely unaffected. This is rather tame; consider the widespread effects of the EMP devices deployed in 'Goldeneye' and 'Ocean's Eleven'.
Answer: I think that in the movie: Alan, Tintin & Fermat are 16, making Gordon 18, Virgil 21, John 23 and Scott 24.