You're right, some (most?) British didn't get it, but clearly some did get it and made public statements to the effect. There's no question Britain left, not out of the goodness of their hearts, but because China has grown too powerful, and Britain couldn't keep Hong Kong even if it wanted to. China isn't Argentina, and Margaret Thatcher had no delusions about it.
your average british joe from the street ''getting it'' and made public statements don't mean anything at all because her majesty's ruling establishment just continued to rule hong kong until the day they were forced out. and you are wrong because Margaret thatcher did have delusions about hong kong. she thought she was going to china in a position of power right after her victory in the Falkland war. it was after her meeting with deng Xiaoping that her delusions about hong kong were permanently gone. I've great respect for the iron lady but she was just a novice in front of a giant like deng Xiaoping.