If you are interested...
Visiting forces - military - uniformed numbers are limited to each 'theatre' of friendly occupation. Therefore in UK & EU as a whole, maximum numbers are agreed. Depending on the operational roles of units, other home nation civilians may be brought in. Sometimes host nation civilians are employed. Costs of keeping people overseas can be great. Each nation is always considering costs (oops sorry getting too political). In the above cases discussed, the USAF has moved to contract via UK MoD for Ff's and other trades persons. This gives them a 'one stop shop' only then dealing with UK MoD and letting MoD worry about running around getting the 'goods'. Over the years changes in numbers of ratios of military/US civ/UK civ have taken place. A staus quo has been retained over the past 15 years, with the odd change such as a higher profile interest at Menwith Hill (and the US wanting more direct hands on control). Utilising DFRS (they have been newly re-named too!) allows the USAF to deploy their military and US civ's to other 'hot spots' as and when, leaving DFRS to cover. (As an aside, the DFRS also deploy civilians to 'hot spots' such as Iraq, Kosovo & Bosnia - going 'in' with the first waves of military, digging their own holes and putting up tents (if they have been given them) and coming under fire!
It seems the MoD fire service, DFRS - Defence Fire & Rescue Service - is now recognised as a F&RS in it's own right, and has/will have enforcement powers as uch as any other LAF&RS.
Amazing and interesting, some things you find out over a few bevvies.