I've lived on a navy warship for a few short periods of time and I wouldn't recommend it, they're certainly not cruise liners, built to fight not for comfort. In a situation like an emergency evacuation from a natural disaster or a war get on a warship, I think in this case you'd be better waiting for somthing a little nicer.
I think the armed forces should help if they're needed and if they can help, but there's better ways for this problem. The fire strike, foot n mouth and more recently bridge building after the floods were events that better fitted the armed forces ability to directly help the british people.