First of all and not wanting to slate the Defence fire service they don't attend too many fire incidents, however they do attend quite a lot of medical incidents if you are interested in that and you may be a little busier if you get a posting on a flying base. I have several friends in the MOD and some of them are now in the process of transfering into local authority brigades because they want to be busier.
You seem to want to join Humberside, what about Lincolnshire? I know when I wanted to join the F.S I applied to every F.S. in England - but after two attempts was lucky enough to get into my local brigade. Spread your wings a little - apply to all your neighbouring brigades, you will increase your chances of getting in.
Good luck in your choice!