US or UK Wedding registry

Neither. Just don't do a registry at all. Asking for money is rude.

Neither. It is very rude to ask your guests to give you money as a wedding gift. If you just don't have a registry, or create a small physical gift registry with a few household items you'd like to upgrade (towels, sheets, etc), your guests will get the hint that there isn't much you need and will choose to gift you cash of their own free will.

Just don't make a registry. Most people just give cash anyway.

Don't have a Honeyfund. Chances are if you're travelling, people will get you cash (or pounds) anyways.

People who want to give you money will likely just give you cash, likely in pounds. A honey fund is a hard no.