I notice the Acer one is £280 atm. After trying my Rift my dad was considering getting an HMD, and that price is pretty good. The inside-out tracking that doesn't require the sensor cameras the Rift uses sounds much easier to set up too.
https://www.ebuyer.com/823549-acer-w...l-vd-r05ee-003
But I wouldn't want to recommend it if they are cheap because they are unusable