Economic benefits
The increase in employment directly attributable to the airport expansion will have a knock on effect on demand for rental properties in the immediate vicinity to the airport. This will not affect housing prices in the whole of the Southend area.
The economic benefit to Southend as a town derives from this increased employment and not from an increase in tourism as a result of the airport expansion. Most inbound foreign pax are destined for London and see Southend as a cheap uncongensted alternative to the other established ports of entry.
Typically the vast majority of new jobs created at an airport will be low paid shift workers (cleaners/retail workers/security/baggage handling). This stimulates demand for rental properties at the lower end of the housing market.
However there must be a reason for the house price increase. Other economic factors for Southend such as turnover per square foot of retail property are down so the message is at best mixed. The council do seem to have spent a lot of money of improving the sea front aspect which coupled with a spate of high end sea front developments being released on to the market may have skewed the housing statistics upwards.
Due to the huge increase in jobs created the airport expansion can be seen as good for Southend but I doubt the airport had anything to do with the housng price increases.