smerel > government appointed official is no more of an authority on Halacha
indeed, this was the case in Lita under Russia. R Salanter was offered a position leading a Russian school system. He seriously considered accepting it so that he could have some influence, but decided to go other way around so that there will be no confusion between government and real Rabbis. I don’t think, though, that this is a situation in England and the Queen did not select who the Rabbi is. Rather than speculating, I am sure we have some chaps here who can clarify.