Has anyone entered the UK on a visitor visa and can remember what documents we need to have ready for the entry officer?

We got the visa 4 years ago so I can't remember the details. Posting in this group because many members have Thai family.

Also, my wife needs to depart Thailand on an old passport to stamp out, but re-enter Thailand on a renewed passport (she's not Thai). Norse only allows one passport number per passenger (and isn't responding to help requests). Can I give the airline her new passport, even though we will stamp out on the old one? Does anyone care if they don't match?

Huge thanks