Andrew Harrison - welcome to "London" - although your airport is in rural Essex.
He claims Cambridge-originating passengers are driving past STN on their way to Heathrow. Yes, they are. Even more are driving past Gatwick on their way to Heathrow, and even more than that are driving past Luton on their way to Heathrow. The same applies to Bristol, Southampton, Birmingham and East Midlands. The only one of those that has much long-haul traffic is Gatwick, which will always be seen as Heathrow's waiting room.
I'm afraid Mr Harrison will be sorely disappointed if he expects Stansted to attract long-haul full-service airlines. Why would they choose his airfield? It's only merit is that he can offer capacity. But he can't offer catchment, convenience or connections.
Never mind - if he stems the decline, and picks up a bit more Ryanair traffic, he could apply for a better job somewhere else!