Driving one with diagram

[JustAGirlStandingInFrontOfABoy]

Leaving supermarket car park and a man was walking across the exit, he was close to be halfway across so obviously I’m waiting for him to cross.

Whilst waiting a car pulls up from the opposite side and pulls right in front of me. I beeped my horn (yes wrong I know, but I’m not perfect) and the woman and presumably her partner just looked at me gobsmacked. I’m the car on the left btw.

Guess so

I don't really understand the scenario I'm afraid. Do you mean the other car was coming from the other direction and got in the pedestrian's way, and that's why you beeped?

I’m taking my driving test in the US right now and this exact scenario came up in my written test yesterday. I knew that you can never overtake another car when a pedastrian is crossing as it’s against state law so I aced the test with 100%. So whilst I know you’re in the UK I’m going to say you were in the right (except for the horn beeping).

The car was overtaking you while the pedestrian was still crossing?

Sounding your horn was absolutely the right thing to do, to get the other driver's attention and alert them to the hazard.