Statement from easyjet.
Due to the delay your flight has suffered as a result of the air traffic control restrictions in Amsterdam today we have missed Southend curfews and will now be diverting into Stansted. Our ground staff are arranging coaches to take you onwards to Southend. Please collect you luggage and the staff within the terminal will direct you to where coaches will be waiting for you. We apologise for any inconvenience this may cause you today.
I thought I had read here that delayed flights were going to be allowed to land at Southend but it seems that is not the case. I do remember though that the council had put in place restrictions on overnight flights so maybe that is the reason.