If you don't like the pricing structure used by your nursery then change nurseries however if they stop charging for bank holidays then the lost revenue will be recovered from elsewhere.
The UK is facing s childcare crisis. In the last year alone 6843 early years childcare providers have closed their doors, surveys have cited rising overheads, business rates, and government policies as the main reasons. For many providers staff are paid minimum wage and cuts are being made to provisions, resources, and opening hours in order to keep the business going, this does result in costs to parents having to be increased.
Funded places here pay approx £2 per hour less than the going rate. Maybe you should petition the government to fund providers properly.