LCY have the right number of staff in place for the passenger throughput, it's Airports 1-01. BAA Airports have been screamed at by all their airlines for not even bothering their arse to attempt this until forced to recently.
You do NOT have to be airside 2-3 hours before a flight, in 17 years of flying I have never *Had* to be airside more than 35 minutes before departure time and that's with a 30 minute gate closure that was never enforced as the aircraft was never on stand until departute -35.....
It's different for the once a year shellsuits though I guess.