I don't think we should have the royals as head of state, but can't get upset about this - Buckingham palace is part of our history and we should maintain it. The reason it's such a fuss isn't that the queen continues to live there while the work is being done - she could easily move out - but even when she's not there they have extensive office staff and government still need the state rooms to be available for official state functions, because the queen is the head of state, 10 Downing Street doesn't have spaces to host the large state functions, the large ones are always officially hosted by the queen not the PM at Buckingham Palace.
I thought as well that each monarch had to sign over the crown estates so Charles could say no if he wanted to. Morally it would be a better position.
Our whole attitude to the Royals is a fudge, we don't mind them as long as they don't cost too much and don't look like they are having too much fun, we'll campaign for loads of shit like leaving the EU as it's un democratic, but there's just grumbling, no campaign to stop the monarch being the head of state. It's odd.