A UPS for Volt Sagging Monitors

So I have an LG 34GP950G and a MINISFORUM MSS-A156. Both monitors cut off when the macerator from my bathroom or my airbrush air compressor motors turn on causing a voltage sag. It's not a huge issue, they just flicker. But it's REALLY annoying, and God knows what's happening that I can't see. It's honestly not a huge deal, all 4 devices are working as intended, just the circuit obviously wasn't wired with all these devices in mind (Garage conversion into an office and ensuite).

So I'm looking for a UPS to keep the monitors from flicking off and on. I've boiled it down to 3 devices that have pretty varying costs.

1. CyberPower UT800EG-UK 800VA, 400W UPS - £54.99
2. CyberPower BR700ELCD-UK 700VA, 420W UPS - £82.99
3. APC by Schneider Electric BACK-UPS ES - BE850G2-UK - £124.97
4. CyberPower CP1350EPFCLCD-UK 1300VA - £229.99

The main reason is my chief concern in all of this: Safety. I don't want to have it risk burning my house down or some other random nonsense - I've seen some pretty spooky videos of people's UPS' smoking and failing. If it fails, it's no big deal, 2 monitors would turn off, but if it started smoking or presenting a hazard then that's a different story. I don't normally like to buy cheap with power supplies which is why I'm asking you lovely people for some advice.

I would just go with the UT800EG but that thing looks so worryingly cheaply made.

The BR700ELCD might be the way but again, looks pretty cheap.

The BE850G2 is a cheap Amazon brand thing so... y'know... all kinds of what ifs with that thing.

Finally the CP1350EPF looks like it'd be the best but man it's such a price jump I wasn't sure if it was just complete overkill and the difference in price isn't going to stop a house fire were such an event to occur anyway.

What do we think?