I cant see their wedding being very expensive to be honest. I picture buffet in the local church hall type
All jokes aside she'll be minted, she has no living expenses and beyond spaffing money in supermarkets she isn't a big spender on makeup, clothes, bags, etc plus his actual salary (and the fact he probably lives at home with very subsidized living costs) and £500k probably isn't out of their reach BUT...
I just don't think she will move out. It's SCARY moving out of your comfort zone and then suddenly to a very empty house while he's at work, being fully responsible for all the cleaning and maintenance and on top of that navigating your relationship. I think they'll be at the Booths til it's baby time personally.