When it comes to headphones, there are three things that matter: comfort, sound quality and microphone quality and comfort. I play a lot of online games so these three things are a must. I have 3x high end headsets and a bunch that are in this price range (I have kids) so I know what good headsets provide, but they come with the price tag. I am reviewing these against others in their price bracket.
The sound on these is not bad, and probably the best in this price range of the headphones that I own. The 'directional' sound in games doesn't come across well, but most headphones in this price range won't do that. For £20 I was rather impressed.
The microphone does it's job. It's not as clear as I would like but for my kids this is great. (The fact that it folds up is also great as one of my kids goes over to their friends house to play Fortnite).
They are pretty comfy for being plastic. I don't think I could handle them for a long gaming session, but my daughters have used them regularly (every day) and I have not had a complaint. They prefer my Steelseries but they are about on par with the Razers for comfort.
The Bluetooh is pretty cool on this...I used it with my phone and it paired without issue...I don't use headphones like that when I am out and about, but my kids will sometimes, and I can see this being a good set for trips etc.
For £20 I think this might be the best under £25 headphones that I have reviewed.