According to an official statement made by Huawei back in December, the update to Android 10 with EMUI 10 on top for its devices would start hitting the UK in February. Thankfully though, the Chinese company has been faster than anticipated.
The P30 series and Mate 20 series devices on Vodafone have already started receiving their updates recently, and today they're joined by P30 and P30 Pro units sold by O2. These should pop up a notification about a 4.5GB update (with an additional 226MB of bloatware O2 apps to be grabbed) any moment now.
If you're impatient and don't want to wait to be notified about the availability of the update, then open the HiCare app, tap on Update, and then Check for updates. Alternatively, go to Settings > System > Software update and do it from there.
After installing, you'll be running EMUI 10.0.0.178 based on Android 10. Three and EE haven't yet released any EMUI 10 updates for their devices, so perhaps these operators are actually going to commence their roll-outs next month. We'll have to wait and see.