Sounding your horn is not going to get the traffic moving any faster

[Lockheart]

So please don't.

I live along a semi-main road which joins with a main road about 400 yards away from my house.

My road has zebra crossings, parking on either side at various points which turns it into a bit of a slalom, is a bus route with three stops between here and the junction, and has a school on it.

It's not the road for you if you want to drive fast. Sometimes the traffic snarls up, usually because a bus is stuck because some pillock didn't allow it enough room to navigate the parked cars / some pillock has parked where they shouldn't, or because the main road traffic is stuck.

Something (I don't know what because my windows are the wrong way) has been buggering up the traffic for the last half an hour and all I've heard is people leaning on horns. I'm trying to work.

Just be patient. Your horn does not speed up time and won't get you anywhere any quicker. It is not a legitimate expression of frustration. Or AIBU?

No, YANBU.
I stopped today to give a funeral (hearse, 2 x limos and then the following cars) a clear route through a quiet residential road without them having to dodge in and out of parked cars and become separated.
The pillock behind thought it appropriate to lean on his horn and start waving his arms at me.

Yabu

Use of horn can bring attention to the twat who is fucking it all up and get them to move out of the way