Last year I did LHR-MAN-LHR before doing a return LHR-JFK flight, also for status requalification. I think the timing was:

12:00: flight #1: depart LHR for MAN
13:00: arrive at MAN
14:00: flight #2: depart MAN
15:00: arrive at LHR
18:00: flight #3: depart LHR for JFK

The LHR-MAN-LHR was on one ticket, booked on ba.com, though admittedly quite pricey. I think around 220 GBP or so. The reason I paid so much was:
- MAN has a reasonable lounge
- MAN has a lot of flights, so even if my 14:00 was delayed/cancelled, I could take the next flight an hour later
- MAN doesn't require any international security unlike AMS/BRU/CDG or similar
- MAN is the shortest distance, aside from LBA, which had infrequent flights
- I really couldn't miss my return flight, so being potentially delayed in Manchester was more agreeable than stuck in Scotland/continental Europe