I've not found any way this can be done but I thought I'd ask in case I missed something.

My about to be husband really wants to adopt my surname after we're married. We'd still need to apply for leave the remain (not ILR) so he can work and stay here.

I think he can probably change his surname here but that it won't be recognised in the Philippines so he couldn't change his PH passport, even after we got ILR in 5 years or whatever it will be by then, I don't believe the PH will recognise a changed surname.

Is this your understanding or do you know of some way a Filipino male can legally change his name?