We almost moved when I was on mat leave (it fell through but not mortgage related, that was approved), we then remortgaged later but I think I had handed in my notice.
We were asked if I planned to return to work full time, and for a letter from work confirming my salary. There was also a follow up question about childcare plans (we said our parents would be having DD) and they didn't look into anything else. It was all quite simple.