That bit is bollox - OP is a British citizen and is not required to pay the surcharge. The healthcare surcharge is for those making an immigration application.

And once you're in, you're in (if your're a citizen or have indefinite leave to remain): "Provision of free NHS treatment is on the basis of being ordinarily resident and is not dependent upon nationality, payment of UK taxes, national insurance (NI) contributions, being registered with a GP, having an NHS number or owning property in the UK. "