No one knows for how long, but there it is!
Getting a PlayStation VR pre-order has not been easy. The first wave sold out in seconds, before anyone had even tried one out for themselves. The second wave, which opened up just as folks started trying the headset for themselves in Best Buy locations, was also sold out in seconds. Sony made it clear that second wave was the last time pre-orders would be available in the US, but if you live in the UK you can get that pre-order purchase in right now.
Sony is selling PlayStation VR in the UK through Amazon and GAME, and both retailers currently have the headset listed as available for pre-order. This isn't through a marked up third-party either. Amazon's retail listing is clearly from Sony and being managed by Amazon. GAME requires you go into a store to pre-order, asking that you put down at least £5 toward your purchase. It's unclear of this is some third wave of pre-orders, or if you're guaranteed to have your PlayStation VR ship on launch day through these pre-orders, but it gets you on the list and lets you guarantee that you have one coming.
Considering how ravenous the buying public has been in trying to secure one of these headsets when Sony makes a big deal about pre-orders, it's not a bad idea to ensure you have a place in line if you want one of these before the holidays.