Without actual dates, you can only begin to guess how busy the flights really are...use:
Away from half term dates, flights I guess would be busy, but not 100% full. Only one way to find out though, and thats to ask when the doors are closed if the flight is full or not.
Quick check on 5 Feb in economy,
319 is S/9 Y/9 B/9 E/9 M/4 H/9 W/4 Q/4 N/4 V/4 T/4 U/? G/4 L/4 K/4 ....not too busy?
277 S/0 Y/0 B/0 E/0 M/2 H/0 W/0 Q/0 N/0 V/0 T/0 U/? G/4 L/0 K/0 .... sold out?
Actually, looking at other flights/dates, LHR
doesn't seem too busy, but the MEL
flights are all very busy.
http://my.flightmemory.com/shefgab Upcoming flights: LGW-OPO-LGW,LHR-FCO-CTA-LIN-LCY,LHR-AMS-GRQ-SEN,LTN-CPH-LHR-ORD