Sounds like you need to evaluate the skills you have and find a job that enables you to make the best use of your accumulated knowledge and experience in a job that is big enough to allow you some personal development. In addition to the RAF firefighting side do you have any general health and safety experience or qualification - risk assessment, first aid, manual handling, coshh,etc?
You could go down the training line, find a job teaching health and safety - its the best way of learning, or for a local authority housing enforcement or as a civvy inspector in a fire brigade if you can tick the right boxes. Or get in on fire extinguishers, sprinkler industry, fire alarm industry for example.
I would recommend the NEBOSH general certificate as a frst step cos its such a good general foundation.