How wrong was I? This thing is amazing! Little did I know that there are already lots of free apps in the Apple App Store that work with it, just search for Virtual Reality!
It's based on Google Cardboard (https://store.google.com/product/google_cardboard) so there's lots of content from Google and others who have used their template.
When you're in a compatible app you need to tap this button to activate cardboard VR:
The image will split in two (1 picture for each eye). For best results, you should hit the cog button and scan this QR code:
Then put your phone in this box:
And hold it up your eyes or use the elastic band (well it is £3) to secure it to your head:
Now wherever you look the image follows you!
Here's a sample from Google where you in a boat in a digital 3D ocean:
Where there's even a huge leaping, splashing whale:
What's most impressive feature of our £3 googles is the built in button which allows you to interact with the virtual world!