Southend is indeed one of the only 24/7 airfields in the London area with unrestricted access. Certainly plenty of room there, though few people seem to have cottoned on to it yet.
The airport operator provide a basic FBO service. They have recently invited proposals for someone to build a full service FBO facility.
Compared to the likes of FAB/LTN/STN landing, handling and parking charges are at giveaway rates
As for journey times it depends where in London you are heading really. The A13 is a much better road than it was many years ago and offers more direct access to the City. Journey times are longer than FAB/LTN/STN though maybe only half an hour or so. Shear volume of traffic and lack of access at some business jet gateways in the London area will dictate if that becomes an acceptable pain
Oh and if the guy you fly has a few million to spare Southend Airport is up for sale on a lengthy lease!
