I was flying to STN as this happened. We were just West of LHR and were vectored West to BONBO (?) (A holding point for the none aviators. I've only been there once before)
We were asked by ATC to hold; work out our endurance and nominate our divert point.
Very professionally ATC didn't anounce the problem over the air but described it as "unusual traffic in the London TMA". It was when we got down that we found out what had happened.
I've flown for 2 UK regional airlines and have been told by both that should we get 'unlawful interference' then we're going to STN. End of! The flight plan's out the window. There's one designated in Scotland too and I don't think that it's a big secret in answer to TOM11's post. Speculation as to why it's these 2 airports would be inappropriate of course becuase there'll almost certainly be many reasons.
I think that the important thing is that plans are in place for every conceivable eventuality and that in this case, as is usually the case it was down to some drunken idiot who'd allegedly lost his mind on alcohol and that thankfully it all ended well.