Vantage update + Jetpack = broken site

I installed the recent Vantage update last week.
It immediately broke my site, which I managed to fix but now I cannot connect to WordPress Jetpack at all.
I’ve deactivated all plugins, I’ve un installed Jetpack and reinstalled it.
The only change is updating Vantage, which has been an absolute nightmare.
Please provide info/a fix ASAP.

URL: http://www.heatongreen.co.uk