LHR-HEL-LHR can be day-tripped for a tad under £400 on most days in November in Club; 160TP return.
LHR-HEL-OSL-HEL-LHR can be had for a tad under £500 on weekends in November in Club/Business with an overnight stop in Helsinki, 240TP return.
LHR-MAN-LHR can be done back to back, or with an hour and a half for lunch and watching the view in the MAN lounge, on weekend days for £270-ish in CE, 80TP.
LGW-AMS-LGW can be done back to back.