I lived in different parts of England for almost 25 years (not originally from the UK). Things I remember registering are
many English people seem very uneasy around death and bereavement, as though it's a somewhat embarrassing thing that only happens to an unfortunate minority. I was really shocked in a couple of workplaces by people not condoling with someone just returned from leave after a parent died, and a neighbour saying people crossed the road to avoid her after she'd lost her dad because they 'didn't know what to say'. See also 'children not routinely at funerals', which must encourage this tendency
anthropomorphising pet animals
approval of the royal family: I'm particularly bewildered by visibly poor people camping out overnight on royal wedding/funeral/coronation routes and waving little flags and buying souvenir mugs, when anger and disbelief would seem a more natural response. (I understand that they're just a longrunning national soap opera, too, but surely it would be possible to have debates about adultery and turnip toffs and pegging etc without subsidising them quite so heavily?)
attitudes to emigration: it seems to be seen as a selfish and weirdly anomalous decision, and to always be about choosing a sunny climate over your family and friends. In other countries I've lived in, living abroad for an extended period of time is an entirely usual thing, and not some unilateral decision that the other country is 'better'
a slightly odd attitude to general knowledge: perhaps because A-levels involve you specialising so young, and dropping what would be core subjects in other educational jurisdictions. A significant minority of people seem to lack a lot of basics in terms of things like broad-outline history and geography, and then say 'Oh, we only did the Tudors and the Nazis'
class: people seem very invested in denying it's still a thing, but I don't see politicians like Boris Johnson and Jacob Rees-Mogg as having the careers they did/do without being 'eccentric posh boys'. There is no possible WC version of either.
education: there's a real cultural anxiety about 'good schools'. Elsewhere I've lived it's been the norm for everyone apart from children with SEN to just go to the nearest school and receive an education that's broadly 'fine' and in line with other schools nationally. No Ofsted inspection reports being pored over, no private options, far less anxiety about it all.
property ownership: I absolutely understand that this is to a large extent because renting is expensive and insecure (I only bought a flat in England because I hadn't been able to stay longer than a year in anywhere I'd rented), but the expression 'the property ladder' always strikes me, because of the way it implies something you're supposed to climb to get somewhere, and the way it seems to damn those who haven't even managed to climb onto the bottom rung as not having arrived in life.
so many of you are incredibly critical of your own country: I get that it's currently not in a good place in many ways, but I generally thought it was a great place to live in many ways, you punch above your weight culturally and always have, and London is a wonderful city, and the network of field paths and rights of way was a total delight and something I still miss.