Definitely.
I'd find it too crass to try and charge guests for coming to my home to eat. However, it's just simple manners to bring a token of appreciation. Because I spend a lot on hosting, guests bring really nice things, flower bouquets, nice champagnes etc. I take something equally lovely to the family member who puts on superb food and hosts on Boxing Day.
If you've done some kind of pre arranged "every household pays cash for Christmas dinner" then it's not a too dissimilar in concept I guess, but it's transactional cash and 100% expected...not based on inviting guests and then showing their appreciation to the host.
It's also very normal to offer to help the host out and not sit about like you're at a hotel all day. Again, that's just manners. You shouldn't have an expectation of showing less appreciation because you've done something to assist the host. Pondering if my DM was expecting her bouquet of flowers back as she did help unload the dishwasher...
I think it's an interesting point too, if you are the host every year. I am. I'm the better cook (at large numbers catering stuff), have the more suitable kitchen and house, and the most DC, so they like staying at home with their new presents rather than being dragged away an hour after they've opened them. DNan, bless her, always offers. Problem is, her house is tiny, no one would be able to sit down comfortably, her kitchen is too small to prep and cook the amount needed for all of us, and actually she's not a great cook at roasts. The little children would be itching to get back home to their toys and there's no room for them to take anything to hers. But none of us would ever say that to her. Just a simple "No no, please don't worry about it, we've got it covered, our treat" is all she will ever hear. So there may be a variety of reasons why OPs offer to host isn't viable to anyone but OP.
I think if you're going to quibble over getting reimbursed £21 because your household contains fewer adults and chose not to drink as much alcohol as the other two households, it's showing very little appreciation to the household hosting you all day.