Yes to butter and slice of good scots cheddar on malt loaf, totally normal supper in my house growing up.
Mushy peas (hot) with vinegar is fairly traditional chip shop side round here. Raw peas freshly picked are also delicious (friends dad had an allotment, I think we are more than we 'collected')
Mashed potato (cold) with coleslaw mixed in is yum.
Mashed potato (hot) with salad cream also yum
Cold rice pud from a tin is just muller rice, nobody balks at that.
Menudo doesn't sound awful, I'm veggie now but it basically sounds like haggis in soup/broth form, we scots love a spicy soup eg mulligatawny, oxtail, scotch broth is traditionally quite spicy and some regions Cullen skink tends to the spicy. We need heating up in the winter up here!
Ah yes - the 70's when brown sugar, processed meat beyond recognition and shippams pastes were 'healthy' 
"Some of these suggestions are actual dinners in this house" yea we've had some odd dinners especially when money was tight or dd was going through a fussy toddler phase (weirdly healthy child on that score - hates choc or chips but once ate coleslaw with EVERYTHING for a month straight, another time took a fancy to cherry tomatoes - had to restrict that one as they have a somewhat laxative effect when eaten by the handful all day 
)
Packed lunches in the 70's often contained dairylee triangles, stock cubes, pots of picallili and jelly cubes just eaten as is - again considered totally normal, can you IMAGINE the fit today's schools would throw??? 
HeyRoly just reminded me of another supper staple - rich tea biscuit sandwiches - 2 rich tea biscuits with either just butter in middle or butter and jam - dunked in strong tea of course.