Is the OnePlus One worth it?

Currently I have the iPhone 4, second-hand, and the earpiece doesn't work, so I can't make calls. It was was my grandma's phone, but she gave it to me as a gift. There's no SIM card in it, so I use it as an iPod. I have a third-hand (is that a thing?) Orange San Francisco. It is about 4 years old and runs off Android 2.0.1. It can't be updated anymore. It has a 3.5" 420p screen and my iPhone has a 3.7" 720p.

So, because I'm 15 now, and I have never had a new, first-hand mobile, my parents said I could get a brand new high-end smartphone. They also said they would put forward £100 towards it. I originally wanted the HTC One M8, but then I saw the price. I then opted down to a HTC One Mini 2 (HTC One M8 Mini), but then discovered the Nexus 5. A budget phone with top end specs, I thought it was perfect. £299 for a 16GB phone with a 5" screen.

I have constantly seen my friends get new phones, (one of them gets a new phone every 6 months, and currently has an iPhone 5s and a HTC One M8!)

It was settled. I was going to get the Nexus 5. Then my friend told me about the OnePlus One. For £269, I could get a 64GB model with a 5.5" 1080p screen. 3GB of RAM, Adreno 330, Snapdragon 801 and Cynogenmod 11s.

So I want to make sure this is a legit phone, and I heard you need an "invite" to get a copy of the phone currently.
Will this be publicly released?
If so, will there be any good Pay As You Go deals in the UK?

Worth it

Worth it, best phone in that budget segment, the second best is nexus 5