Please consider that it is the solenoid on the starter rather than the battery, it's happened to me a couple of times. Initially I thought it was the battery despite good voltage as with a fresh, or newly charged battery it always started with the extra juice. Now I've learnt the lesson.
And try Toaf, as you've a newer 75 you'll need the small Autoliv SRS Tool
http://toaf.roverki.eu/index.php/en/download-en), a Windows computer running Vista or higher (Win10 works) and a VW type KKL cable from eBay with pins 7 & 8 bridged. Very easy to use, even I manage it
Regards