Heathrow,
Old chap. I know we have quite a few airfields, in fact in these days of financial squeeze I find it quite hard to believe how many we (well...the RAF) have hung onto - different thread perchance.
I disagree with your point about being able to build them quickly. I don't think we can. There are aeroplanes that can operate off bare bases, I remember a very capable one - but we got rid of it. What's left requires well found bases.
Also. Let us be sensible. The UK FW FE@R is now so low that we shall (a la ELLAMY) deploy to a single DOB. That makes GR4 and Typhoon at Goia as vulnerable as F-35 on QECV.
In short, our eggs will be in one basket in any case. Why not have a moving basket that the baddies struggle to pinpoint and no-one gives us permission to use?