This is so unnecesary. I've been commuting between one of these said commuter towns and London for the last 12 months on a regular basis, as well as flying 2-4 times per week ex-LGW. I pay 10% extra on my season ticket for the privilage of using the Gatwick Express when convenient.

The reason the GEx trains run half empty at peak times is because the timetable is arranged to make it worthless switching to the faster train at LGW.

For example:

A semi-fast Southern service from Portsmouth to Victoria via Horsham and LGW stops at the airport at 25 past the hour, then runs via Redhill, East Croydon, Clapham Junction and Victoria in 43 minutes.

There is a Gatwick Express leaving the airport at 35 past the hour, taking 30 minutes.

So, staying on the overcrowded Southern train gets you to Victoria 3 minutes later than if you switch.

The timetabelling is for competitive reasons - why should two companies collaborate and integrate their timetables when they are competing for the same customers? Why can't a non-stop GEx depart approximately 1 minute after each semi-fast Southern arrival - it would still be 4 GEx per hour?

GEx is one of the factors that makes flying ex-LGW attractive.