I use mostly Sonoff, Aqara and Ikea, but I have a variety of other brands as well.

Sonoff is cheap and reliable, a few of their sensors have a the odd quirk but have worked well overall.

Aqara have more features and a more elegant physical design, but can be bit more expensive - although still cheaper than some other brands. I have a lot of their temperature/humidty and contact sensors and they look nice on my walls and windows.

The one problem with Aqara devices is they don’t properly follow the Zigbee standard, and don’t play well with some other brands, leading to constant disconnections. They do work fine with Ikea devices however. I had a lot of problems until I split my Zigbee network into 2, one with only Aqara and Ikea devices, and one with all the rest.

I’m also using a few devices from Samotech and Aurora, who have some good UK specific Zigbee devices such as rotary dimmer switches and smart sockets.