there have been situations where rail staff have gone into a carriage on fire and been overcome with the smoke. i would have to assess it before just playing super hero (when no public are at risk)with a fire extinguisher.
455s have a couple of banks of large fire extinguishers in each cab/cab vestibule, but
physics34 and
OFFDN have correctly posted, it would have been extremely hard or impossible for a member of train crew to put this one out. At least one previous fire on a multiple unit on the Southern network (or, rather, one of its predecessors) saw a member of staff lose their life after trying to tackle it; sometimes it is neither possible nor worth the risk.
I'm not sure if you're actually aware of the configuration of a 455 body-end cupboard, but it's a fairly large space and more than enough surface area for a serious fire to take hold in there before starting to make itself properly felt and visible in the saloon. Just like what I suspect happened with the fire on the 377 at Eastbourne (partly from photos seen on here, in fact, as well as others), this fire probably spread within the void behind the interior panels before the full facts became known.
Once the driver was aware of a fire (which, at that stage, would probably have caused various fault symptoms in the driving cab before too long anyway), it
seems like their first priority was to make an emergency call and then evacuate the train at West Croydon, where it was stood - that was the first set of actions I was made aware of. This was a good move.
Lastly, what I'd also say is that certain stock does need a number of further actions taken to make some of the covered electrical equipment safe before approaching it, for example in the event of fires in body-end cupboards. Isolation is not always enough. Even diesel stock is not immune to this.
Can the equipment cupboard be isolated internally or would the driver have to paddle up and tie off each shoe in turn (would just the removal of all shoe fuses be enough to properly isolate)?
In this case, fitters needed to be dispatched to isolate the relevant shoe gear.
Does newer stock have the capability for shoe circuit breakers to be operated from the TMS?
You can do various things, including remotely raising the shoes, on some stock but the ability for fitters to remove shoes in-situ generally remains.
455s are relatively primitive beasts, and as you probably know, don't even have TMSs.