Anotherthing,
Well the last time NATS lost a contract (Prestwick) I don't think there were many takers to go to PIK.The new controllers were sitting with airbands listening to what was going on ready for day one.

I would like to think that NATS would give the option to people to move,after all we are a mobile grade

and a valuable highly skilled resource in world wide demand.
There is also TUPE for people who wish to stay put.I think changing ATC suppliers at the busier units is almost impossible nowdays with SRG and all the rules that apply.
In fact even a small reduction in the number of staff at the smaller units,can have a drastic affect on the service provided.Any newcomers would have to be pinched from other units,but since NATS will have got rid of the good pension,then where are they coming from?
You just have to look at the ads in Flight and there are lots of jobs for Approach,Approach Radar and Tower qualified ATCOs.
But then NSL isn't up for sale.The management say so.