25 years in the RAF including over 8 years at one of the units in question and numerous visits/dets to the others.
The only one I have no person knowledge of is Yeovilton.
With the extent of privitisation you would be surprised at the number of civilians wandering around a base these days. Unless someone was obviously carrying cameras they could quite easily roam around.
Access to anywhere like a PBF, WOC or HAZ complex or other secure area is, however, substantially more protected!