"I also wonder how a Kenyan style attack would play-out in the UK."
Badly. The police would take a while to get there, surround the perimeter
and contain but not enter, deliberate over what to do, argue over which agency
would do it, wait for the Gov't to authorize the use of the military etc etc
Re an out of the blue SF attack, unless you ring the base with people 24 /7,
any good SF troops will find the weak spot and plan and prepare enough
force to get in. As to what happens from then on, ..................