There is a bit of a difference as overbooking if carried out is by one or two seats only and allows for no shows so I doubt if anyone is routinely kicked off a flight as most flights are not full and those that are will have passengers who have not turned up so allowing for those overbooked to find a seat. What is going to happen is the mass expulsion of passengers due to a weather issue that for Easyjet is unique to Southend and won't happen at Gatwick, Luton and Stansted in the London area. That is assuming the flights are nearly full.