Hi! I'm also doing politics A-Level, but I did the UK exam last year so apologies if I'm a little bit rusty. I interpret 'important' as sort of the same as 'influential/significant,' so it's not asking you if it's good, it's asking you to what extent they are currently impacting how the government functions.
I think what you've written is pretty spot on to be fair.
Ministers resign because of IMR = important
Some don't, undermining IMR = unimportant
Undermining IMR can make the government look weak, and affect public trust/chance of re-election = important
The only thing I would say is that that is focused on IMR, but the question has asked about CMR as well. Your response would be very similar. For CMR, it is important because it ensures that discussions are kept a secret from the public, and presents a strong government. It is arguably unimportant because some members may choose to resign rather than
Cabinet discussions are kept secret from the public = important
Public perception of strong government = important
Some Ministers may resign rather than uphold CMR because they disagree so strongly (e.g.: Theresa May lost 17 Ministers over Brexit) = unimportant
However this can significantly impact the strength of the government, public perception of the government, and could lead to a vote of no confidence (as seen in Callaghan's Labour government in 1979) from Parliament = important
I hope that that helps a little bit? As I say, it's been a little while, so this may not be spot on.
If this question has come up before, check the indicative content on the mark scheme, as it's usually pretty helpful. Good luck!
