The only general difference between an Irish and a British breakfast is that one is eaten by a ginger-headed freckled person with a hangover and the other is served on silver platters by people from below stairs to people wearing morning attire .... I think you will find ...
Funny, but not actually true
An Irish breakfast features black and white pudding, and an Ulster fry (from the north) usually has soda and/or potato farls. Mushrooms and baked beans on the other hand shouldn't feature (although hotel buffets frequently will have them).