One of the more depressing features of this thread is the sheer ignorance of the workings of the airline industry displayed by some of those who make the most noise. Some of the preceding posters seem completely unaware that many airlines use a deliberate overbooking policy as part of their normal commercial operation. Such an airline will probably have an overbooking profile for each route based on its operational experience. The aim is that the number of seats overbooked should equal the number of no-shows. In this way revenue is maximised. When as sometimes happens all the pax turn up, then the airline is into offloads rebooking, hotels, EU261, social media even perhaps the mainstream press. Its the commercial risk the airline takes. You may not like it but it is common practice.
To imply that it is only at SEN that you will get bumped off is nonsense. EZY clearly have an overbooking policy (though I have no knowledge as to the details of its workings) that may apply anywhere. This article shows the policy coming unstuck for EZY at other well known London area airports.
https://www.theguardian.com/business...enied-boarding