It will be interesting to see how this works out.
Canary Wharf - Stratford - SEN is an easy journey. It is a slightly captive audience though. If one needs to travel Berne-London, it would be a case of chopping off your nose to spite your face if you switch to Basel (about 1 hour drive from Berne) because you don't want the 45 minutes extra train journey, some of which will be offset by the flight being a few minutes quicker.
At the times the flights operate, pax will be through the terminal in no time.