Well I've downlaoded an app called Wifix, which was free, hit the fix auto button, set my phone never to go to sleep in case it turns of wifi during sleep, and that fixed it.. So far any way. We are up to 111 out of 1127 tracks, which is a big improvement over the 20 or so it topped out at before.
Yeah so now I have all 1127 tracks synced to my phone and playing nicely :) Which means it wasn't spotify's fault at all, it was my phone losing internet connection independently to spotify. Awesome.
Thanks spotify for your support, I am not sure if this was a case of multiple faults (such as me syncing too many devices and you showing me how to delete some) or not, but it's good to see you guys supporting me to reach a solution.
Stoked to be able to listen to the pixies at the gym again