Jack replied
Hi,
Thank you for all of you help.
We have been working on the site all day and got the PageSpeed Insights Score to 96 Desktop and 65 Mobile along with a 98 GT Metrix Score.
In case it helps others, we ended up needing to in add the CDN address into WP-Rocket (I believe there is a similar setting in W3 Cache), that resolved most of the render blocking errors and substantially increased our page speed scores.
Thanks again for all of the help,
Jack