I think the EZY situation is different from most airlines, the management are highly focused towards the on time performance, I also believe that Easyjet also have a framework contract in place with Menzies that covers more than just the UK.
I am old enough to remember when Britannia had a similar deal in place with Servisair, there was always one station outside the deal for whatever reason. It used to be Birmingham and then when Servisair Birmingham won Britannia Servisair Newcastle lost it.
In summary I believe it’s up to Menzies who looks after EZY in Bristol