Following the sudden impromptu aerobatics, the captain advised us that we were returning to Guernsey. No explanation of the cause was offered. No injuries that I know of, a few spilled drinks though. The trolley was well behind me so couldn't see what happened there. All professionally handled by the crew. We got a straight in approach and no blue lights seen on arrival. After arrival one of the groundcrew told me there had been an icing problem. Not a lot to report I'm afraid. Got airborne again a couple of hours later.