I was also given an op-up LGW - JER last friday. Checked in to 6A and was told at the gate that I was being upped to 1E. I didn't even think that CE was on the Jersey route and was just about to moan that it wasn't really and upgrade to me as I prefer a window seat. Anyway I didn't really have time to do or say anything and just carried on walking with my new boarding pass.

On board the E seat wasn't too bad - the flight was only 35 mins and had a nice salad and glass of champagne so I can't complain!

There would have been no chance to refuse the op-up because ET was rammed to the rafters. Even on such a short flight I think you'd be crazy to try and refuse anyway.