How common is it to say "I am sat" and "I am stood" instead of "I am sitting" and "I am standing"?
Recently I encountered these expressions and I'm wondering if the majority of people in the UK use "sat" and "stood." Also, are there any other instances like these? I mean beside sat and stood?

Question

Answer

It is informal British English.

Here is a recent discussion:
https://www.italki.com/question/484302

Answer

No, "I am sitting" and "I am standing"? are present continuous.
Sat and stood are past tenses.
I sat down, then I stood up then I left the room.

I do not know any grammar but I think sat and stood are in the Preterite tense, one of the past tenses.