Problem we had years ago was when our dentist stopped NHS work we had to have a check before we could go onto Henllan.I had exactly the same scenario. Re-register and join up for a scheme where a set fee was paid every month which allowed you two six monthly checks each year and obviously any treatment on top of that would be extra. That was a couple of years ago and I didn't bother.
I had one email from the practise asking if I wanted to sign up and nothing since. As far as my teeth are concerned, so far ao good.
Anything found was not eligible for the plan.