With regard to being chippy - you do seem to have an anti-Southend view Skipness - WHY???? The"demographic" for Southend - at a guess - will be the relatively well-off areas of South and mid-Essex and the teeming millions of ( some very) well-off leisure / business users in East London. A totally mixed bag.
The demographic will proportionally be biased far more towards outbound as I suspect SEN might become the local airport of choice for people going on holiday and serve the community well. That's nowhere near becoming a strategic asset in serving London which is what I am questioning, and indeed I would be surprised if that's what the town wants.
Essexman you can be as close as you say the square mile but if that's not the market that ends up using the airport, then that's not the issue. I am well aware where the other airports in the area are thanks. I know how far Canary Wharf is from each airport as I live five minutes away on foot from South Quay. You realise that with your personal example, you're kinda making my point for me? No?