I should probably add (wandering a bit off the topic here) that the only place I have seen the U2 code used is at Nice airport, on boarding passes and departure boards. The BH code is never used: it did belong to TEA Basel AG, which became easyJet Switzerland, so I presume it still exists. All flights operated in the 900 range are "operated by easyJet Switzerland SA", according to their timetable. End of digression.
I see that the cheap Easy Saver flights with SWISS to LHR that I managed to secure 2 days ago have well and truly disappeared, there being no availability for 3 days either side of my dates. So, they're selling well. To be quite honest, you will have to be extremely quick to snap them up. EasyJet is the same: there are very few of those cheap seats, and you have to grab them jolly quickly, usually a long time in advance. Most of the time, I kid you not, I am getting a better price (or as near) from the full service airlines, plus miles etc.. And how generous will easyJet be in rerouting you from LTN should there be a technical problem or major delay with the flight?