As far as I know this is similar to my partner's deal and the most expensive thing is a crown and only the fabrication of that is not included, the rest of the treatment for it is in the plan.
If you need a simple crown that is subsidized if not completely by the NHS you'll be able to offload it to the insurance pretty easily, if you want the top of the line ceramic crowns that cost 1500-2000 GBP no insurance will actually cover that.