Welcome to Britain Mousa Kousa. You may have been a torturer, a facilitator of terrorism, but that's all in the past (two weeks ago, in fact). Now you're a democrat, a defender of freedom.
How are you going to play it, Moose? You're going to have to talk to the CIA, and they'll want you to confirm that Libya was guilty of the Lockerbie bombing. But that's as good as saying that you planned the atrocity. Deny Libya's and your guilt and you'll probably be cut loose, no anonymity, no round-the-clock bodyguards. Confirm it, and what? You'll be surprised how forgiving our rulers can be. No doubt a script is being prepared for you that will point the finger at Libyan intelligence while showing you to be free of all blame. Perhaps, like Kurt Waldheim in the Balkans, you were on sick leave at the time.
The British government has stated that you do not have immunity for past offenses. Don't worry about that, nobody takes any notice of British government statements, They're just intended to give the press something to print now that now that news gathering is unfashionable.
Here's my advice, though an old stager like you won't really need any. Give them Gadhafi and his offspring; movements, location of bunkers, etc. But first tell them that they can't trust the contenders, Abd-al-Jawal, Tarhuni, Mesmari (Sarkozy's boy). Promise them that if they ease you into the top spot the steady flow of cheap oil is guaranteed.
Home and dry.