The simplest of snacks, but can be a bit of a delicacy when it's just right. My favourite at the moment is Vogel's Original Mixed Grain with Lurpak butter. With a cup of tea of course.
I have overnight oats (with my own in-house seed and fruit mix) on weekdays but Saturday and Sunday are butter on a nice white toast days
After visiting Oz in the early 90s, I made the switch from Marmite to Vegemite but I've reverted to Marmite for a couple of years.
However, I never have Marmite on toast for breakfast, it's reserved for a late night snack. My breakfast consists of a single slice of white sourdough bread with shred-less orange marmalade.