So I took it to the dealer and after explaining to them what android auto actually is!! We plugged the phone in and it worked. 10 times in a row....I hate intermittent problems .
So the guy said there was nothing they could do since it was working now but to bring it back if it stops again.... Getting the S7 edge next week so will wait and see how that works.... Apologies i haven't got a better answer for you...
Just the kinda luck you need Well, thanks for the update anyway. If you happen to visit the dealer again regarding this, let me know.
In the meantime I might book service myself to see if they can do anything.