Installed new SSD on Macbook Air now won't let me reinstall OS
OK so ultimately I was able to solve the problem and here is how.

I noticed that when tried to install OSX straight away it failed but when I selected a drive that had OSX installed on it, it validated successfully. However once I had erased the drive it no longer contained a copy hence validation failed. I still had my old SSD which contained a full copy so when I plugged that in via USB and selected it in startup disk, the installer validated it and allowed me to install OSX on the new drive.