Overtime ban or AAVA ban?
Swanwick TC doesn't allow part time ATCOs to do AAVAs nor operational overtime (and I have a feeling it doesn't allow part-time overtime full stop).
AFAIK AC doesn't allow part-time AAVAs - however it has in the past allowed operational overtime (under the less lucrative overtime payments regime). I'm guessing that it is this that has now been banned or maybe just brought into line with TC?