"Tea" was a meal that I rarely took - usually when invited out to someone's home, or at my own home on a Sunday. It consisted of bread & butter with jam, fish- or meat-paste, and a cutting cake

Yep, definitely my main association, Rhuby, probably making this mainly a Southern (English) thing. Tea's more of an extra than a standard meal, often associated with holidays. You can have several different types of tea, though - I'd think can of pink salmon rather than fish-paste, for instance, and "posh" teas probably would include little dainty cakes as well as the cutting cake(s), etc.

Tea is often a follow-up to a good hearty lunch, and may include cold meat left over - this especially applies to Christmas tea, where you also have other cold meats (say ham), pickles and whatnot (yum!). But tea's generally more sweet than savoury.

However, I have to say that sometimes it doesn't feel right calling my evening meal (8pm-ish) "dinner", and it's too early to be called "supper". It depends a bit upon how casual an affair the meal is, and how much effort it takes to prepare the meal, but "dinner" is definitely more like meat & two veg than Spag Bol. Spag Bol would be "tea".

Similarly if I'm getting home early enough to have fish & chips () with my family - say, 6pm - I'd definitely call that tea. I'd also drink tea with it, but that may be by the by.

Of course my wife is a Brummy so I may just have been corrupted by her North-of-Watford influence.

Oh, always "lunch" for the midday (-ish) meal for me, BTW.
"Dinner" is always an evening thing (often special occasion), and "supper" is a very occasional late night extra. After-pub snacks don't qualify - it has to be a sit-down meal, cooked in the kitchen, that you eat around 10pm.

Come to think of it, I'm not sure I've ever had supper.