Xiaomi Warranty in the UK

I just got off the phone to Xiaomi UK and they said that their phones have a 2 year warranty on them if you buy from the following;

Xiaomi store (Online / Westfield)
Three (3)
Amazon
Argos
John Lewis
Carphone Warehouse
Currys PC World
Very
Go Mobiles
Mobile Phones Direct
Ebuyer

If you buy from eBay it won't get the 2 year warranty. I'd assume you'd still be able to get the warranty if you bought second hand as long as you could validate proof of purchase, i.e get the original reciept.