I do know that knights were addressed as sir and their wives (if they had one) were addressed as Lady.
Most others below Princes were addressed as Lord (as in yes m'lord)
not sure if that is the official way of being addressed.
Dukes were addressed as Your Grace, His Grace and Duchesses addressed as Your Grace or Her Grace
Kings and Queens were addressed as Majesty or Your Majesty
and Princes and Princesses were addressed as Highness or Your Highness
Sire was also a way to address those who were known to be of higher rank than yourself, but you weren't actually sure just what that rank was. Better to be safe than sorry
also there were Lords and then there were lords, as well as Lady and lady, depending on the rank.
I also know that some peers and peeress were master and mistress,
Also you have them ranked in the right order of importance for the most part. I am not sure that this had anything to do with it back in medieval times, but when Sarah, Duchess of York was married to Prince Andrew, she outranked Princess Anne. I guess it's all in who they marry. Fergie only outranked Princess Anne because Prince Andrew was third in line for the throne while at that time Anne was 5th in line. she's gone down since the Duke's daughters were born and Prince Edward had children.
if I remember right a duke's son is known as a Marquess. And an Earl's first son is known as a Vicount and second son's are known as Baron
An Earls wife is a Countess, in Britain there is no such thing as a Count. in other countries however, I don't know
personally I think it's just a system that developed so each level could say "I'm better than you"
bits of trivia that has stuck in my head over the years from all the odd things I read