The interview went fine, of course, and Jen's shiny new maroon passport turned up in the post a week or so later.
She was asked to describe the floorplan of our house (presumably to make sure it matched the one shown on the RightMove website). She was also asked how many miles it was from our front door to the Eden Project site (correct answer: I don't have a clue) and why she'd kept her maiden name when we got married (correct answer: none of your fucking business).
Still don't see what all this is supposed to prove, but as long as they're happy. And Jen says her interviewer was a very nice woman.