Which trade(s) do I need - plasterer or decorator?

[TheOneWho]

Long time lurker, but now I'm hoping the collective wisdom of Mumsnet can point me in the right direction.

I have noticed quite a few cracks appearing on my walls, in different rooms. I've attached some photos, which hopefully give an idea. Most of them look like the paint cracking/peeling away under/above the coving, with others along where the walls meet the ceiling. We haven't decorated since we moved in a few years ago, so I'm hoping it's just cosmetic, but would this require a plasterer, or would this be within the remit of a decorator? Both? Neither of us are terribly handy, so would prefer a professsional.

The property is a first floor flat with the loft above. The neighbour below has a habit of slamming doors, so I'm not sure if it's vibration/movement that has caused some of this?

I'm not sure if this is in any way relevant or connected, but over the last few months one of the rooms affected by the cracks has started making some strange noises. This sounds like the ceiling is 'shuddering' like an air wave is passing over it, with the noise bouncing around to different spots. It doesn't happen all the time, but seems to mostly be at night and worse when it's warm. It's not pests, and the roof has been checked and appears to be fine. Any ideas?

These look like minor cracks that a decorator could easily sort for you

Definitely a decorator. You can do this yourself too if you want. You can buy ready mixed filler, a spatula/scraper. Just fill the holes up, give them a sand to smooth and then paint over. Very simple. Lots of videos on YouTube.

Thanks both. For the third photo where the cracks are around an inch from the wall/ceiling joint, it's possible to press on the crack and see it move, is this still an easy fix?

A tube of caulk from B&Q and you can fix this yourself in 15 mins.

Yes, cracks usually move when you press them because a gap has opened up. If you wanted to be ultra, you could replace all the coving. But I wouldn't bother. Cracks do appear over time so no matter what you do, it is likely to come back because houses live and breath. If you want to, you can use a Stanley knife to open up the crack and make it bigger to get more filler in. It all depends on how expert you want to go with this. If you find it too overwhelming yourself then a decorator will easily be able to handle it.