It should be a 2 year warranty if you purchased it in the UK.
I got it from AliExpress from the mi store. I've email them. Hopefully have a reply tonight
I've orded a Poco F3. After checking the specs it's not much of a upgrade but I need a phone for work and it's pointless buying a temp phone.
Updated: so I bought my phone from AliExpress 12 months ago. Xiaomi UK are honouring the warranty and sent me out a return envelope. Going to send it off Monday. They said it should be 3-5 days.
Bought a poco f3 anyway. It is nice, but pretty much a side grade from the f2.