Amen brother. With great respect, I'm not sure that you understand how the air traffic system works. Developing Northolt would not necessarily make any difference to delays at Heathrow as it's an airspace problem. The same aircraft are going to have to fly the same routes so the same problems arises when they get airborne. Inbound aircraft to Northolt which fly the airways system are treated like Heathrow inbounds so, far from reducing landing delays, the problem would be exacerbated if Northolt had a significant increase in traffic.
Northolt is far to close to Heathrow to make any significant difference to road problems - have you tried driving through Hayes at rush hour?
Also, as mentioned earlier, the runway configuration is far from ideal and would be unsuitbale for anything heaver than the existing business jets and military aircraft which frequent the place.