EssexMan - it is certainly possible that Southend-Berne will do reasonably OK over the next few years, and anyone who absolutely rules out this possibility is almost certainly ignoring the unexpected.
However, it's worth remembering, that if an airline flies aircraft with 33 seats, they need to charge premium fares. Skywork between London and Berne do not offer cheap tickets (although they sometimes have fare sales for bookings made in the few days around Xmas and Easter). The lowest normal return fare for Southend-Berne-Southend is £181. Skywork will likely want to sell quite a few tickets at a higher price if they are to make a profit.
Berne airport does not have a train station - one must take a taxi or bus to Belp, and then a local train to Berne to get anywhere.
Zurich airport has a large train station with excellent service all over Switzerland, as well as superb connections at Zurich's city centre train station
Direct trains run from Zurich airport to Berne city centre twice per hour and take 1h15.
Someone who is price conscious will likely choose Easyjet between Gatwick/Luton and Zurich. Those who can afford Skywork's fares may be looking additionally at BA or Swiss on the London City (or Heathrow) - Zurich route, followed by a train to Berne or elsewhere in Switzerland.
It's worth noting, that from Caen, Rennes and Groningen, it takes typically over 2 hours to reach the nearest hub airport with trains operating at a much lower frequency. Trains run from Munster to Dusseldorf twice per hour and take 1h20.
One cannot rule out the possibility of Skywork doing OK at Southend, but in moving from City to Southend, fewer of Skywork's typical passengers are likely to be interested in their offering and the airline will have to devote more marketing resources to keep yields and load factors healthy.