http://download.yamaha.com

Select your country
Type in your MODEL NAME
When the SEARCH RESULTS appear verify by clicking on the MODEL NAME

A list of downloadable items for your instrument will appear.
The download include instructions. Please read through them before attempting update.

Thanks for your very quick response, much appreciated.

So Im guessing due to the lack of Os1.50 on the Yamaha site means theres a couple of bugs being rectified before re-release?

No need to guess

https://yamahasynth.com/forum/can-t-seem-to-find-the-1-5-firmware-download-link