No idea what the situation is at NCL. But the fact is that experienced ATCOs can basically go wherever they want now. So the smaller units are naturally going to struggle.
A few years ago the gaps were being filled by military ATCOs retraining. That seems to be drying up. Then there were queues of self funders with Student ADI tickets, that seems to have dried up too, especially now the cost of a course has doubled...
There aren’t enough ATCOs to meet the demand in the UK. Ultimately, if regional airports want to prevent their Controllers heading elsewhere they need to make their units more attractive, or they will not retain staff. It’s as simple as that...