Anyway, I have been on the Beta for almost two days and seeing no worth to being in Beta so thought I would go back to stable.
I took a while to search XDA and OnePlus community and found some saying you need TWRP and other saying you cant.
The answer is quite simple and thanks to @Cave_diver for directing me to what actually works
There is a rollback file at https://forum.xda-developers.com/sho...04&postcount=2.
This takes you back to Oreo but will immediately update you to Pie.
It will wipe your data and you wont be able to auto restore your google pie data initially but once update, factory reset again and then all good.