Gutted to hear this mate. Im in the fire service in London and have never heard of this happening before.
When reversing an appliance (fire engine), there has to be at least one person at the rear to see the driver back. This person must use hand signals and shout out if the driver is getting close to anything.
In my experience, there has been the odd occasion when the person at the back shouts out but the driver doesn't hear first time. It sometimes takes a second or third shout which can be too late.
This may be due to the fact that the person at the back is usually in a quiet environment and believes their voice is sufficiently loud for the driver to hear, but the driver is sitting on top of the engine and next to the officer in charge (who may be sending verbal messages over the radio), the heater blower would normally be on full blast this time of year and the switches and relays for the blue lights make quite a lot of noise. This obviously is no excuse but may be a contributing factor.
If they have tried to leave the scene without taking any details then that is unacceptable and I would hope that this is an isolated incident. As for your insurance, I believe London's insurance company are fairly quick with any claims but don't know about Suffolk. Don't worry though, you won't have any problems.
The firemen responsible may be retained (part time) in your area and have another profession which they earn more money in but this is no excuse for leaving the scene of an accident.
In East London we work with the police and ambulance quite a lot and we have an excellent relationship. As for the lazy slackers bit, I suppose you could find a few of them in any profession. And as for moral fibre, I don't know any firefighter who I wouldn't put my life in the hands of.
Anyway, hope you get it sorted out mate