@Aintnomountainlowenough I’m actually from a communal country where I can guarantee our funerals, weddings, etc are at least ten times the size of UK ones. But
(1) In my home country we all grow up together, live together, help each other out all the time. If your household is already like something out of Coronation Street I’m sure the presence of your close neighbours will be comforting to you. Here, that is not the case. It’s as good as holding the event with random strangers on the Tube. Intrusive, painful and awkward. Sorry but you can’t just decide to magic up non existent closeness and kinship overnight.
(2) There are spheres of community. In a communal event, others close to you but still not the main bearers of grief bear the burden of hosting, arranging, and even distracting other visitors.
Again, this is clearly not a communal event and so that burden will fall solely on the grieving family. Of course I am sure / I hope the gf is not expecting an elaborate warm reception but as it stands it’ll still be awkward and random having a stranger floating around in one’s own intimate moments without anyone as your privacy “wingman” (as I’m sure you’d know happens in any huge communal event).
(3) Finally, even in communal countries, there are community things and there are private things - private ceremonies after the funeral, and being with the body being the latter for my family, as it seems to be for OP’s family. As I’ve said multiple times, this is clearly not an open casket thing. You yourself talk about Day 1 and 2, suggesting Day 1 is more of a private affair. Another analogy could be that baby showers (or 100 day baby birthdays, which are massive events where I’m from) are not the same as giving birth. Just because some people hold huge baby showers doesn’t mean you can muscle in on the birth itself…