Pretty much agree with most of everything here. Signature good, a lot better than most other UK Signatures. OCS good also. Not used Harrods, though I'm told don't park your car there, is this still true?
I like the Hoo, but very remote. Dislike Luton immensely so may try your suggestion pirate. Sometimes get the train to St Pancras which is pretty easy.
Miles I have to comment on your post. Been to Cranfield a lot, and the poor excuse for an FBO was very poor. Did nothing to justify their cost, parked miles away from it, didnt even get weather from the staff. No where close to sig Luton levels of service.