*puts on scholar hat but with the disclaimer I'm not actually a scholar just a history nut*
Winterlight is correct about the Church of England and that Edward VIII, as Supreme Governor should have been seen to uphold the rules of the church and therefore really had no choice, it was Wallis or the crown. I don't think too many people in the government objected much to his abdication as it was known that Edward and Wallis supported Hitler which is why they were sent to the Bahamas during WWII to keep them away from Germany.
As for Camilla, what a lot of people don't realize (or want to admit b/c of the great love for Lady Diana) is that no matter what she is called after Prince Charles becomes king, Camilla will still technically be the queen as a woman married to the king does not have to be crowned in order to be called queen. A woman always takes the title associated with her husband; there are many examples in various monarchies around the world of this (i.e. Jane Seymour & Marie Antoinette), often if a king marries after becoming king, there's not always a crowning ceremony for his wife who is still referred to as the queen. The decision to not call Camilla "Princess of Wales" or "Queen Camilla" is purely a political one.
However, if a man married a queen then he is not known as "king" unless the queen decrees it. If the husband of a queen is named king consort, he does not have a right to succession and would, upon the death of his wife, have to succeed the title to his son (or daughter) and be styled in a manner similar to that of the Queen Mother. A queen could bestow on her husband the title of crown matrimonial which would mean that he was, in effect, her co-ruler and would keep the crown after her death until his death.
Most famous of someone being named king consort but not given the crown matrimonial would be Lord Henry who was married to Mary Queen of Scots. She made him king consort upon their marriage but didn't want to make him a co-ruler which ultimately lead to the breakdown of their marriage and his assassination because he wanted the crown.
Another good example is Ferdinand & Isabella; after Isabella predeceased Ferdinand, he lost the title of King of Castile to their eldest surviving daughter who was her mother's heir, not Ferdinand.
Why yes, I do read a lot of history