New bike but no idea on inner tube size I bought a new bike a few days ago, Cannondale Bad Boy 3 2019 which gets delivered in a few days. 

https://www.cannondale.com/en/Europe/Bike/ProductDetail?Id=7f48452b-f9eb-4e10-89e7-4a7550944bfa

Buying the spares I'm at a complete loss on finding the right inner tube size, popped into Evans Cycles today and the guy wasn't much help at all.

Anyone able to tell me and possibly link me to the correct inner tube's required?

Cheers!
The required spec is on the page you link: Tyres: Schwalbe Kojak Performance, 650x35c.  If you go into a bike shop and ask for 650x35 tubes they'll give you the right size (probably 650x32--38 as tubes fit a range of widths). 

The only problem is that the valve type isn't specified there.  It's almost certainly Presta, but there's a chance it's Schrader (car style).  Strangely zooming way in to the photo, there's no sign of the valves at all.  You might want to hang on until you can check what valve it's got.