EY/QR/EK
MM
It is possible to compare with all UK airports but with Heathrow you have more than one airline in some cases and different types of aircraft with different configs and I haven't got the time to dig that far. Here is a quick compare.
As for Dubai in January
BHX 42834 - 345 pax per flight 83% load factor
GLA 24167 - 390 pax per flight 91% load factor
NCL 14331 - 231 pax per flight 83% load factor
LGW 51379 - 276 pax per flight 80-83 % load factor
LHR-Doha 61077 - 246 per flight - 80-85% based on 77W/332/333/346
Pete