Thanks for taking the time to look at this.
I have finally found the solution... I have this working as I want now.
It was to do with the static routes yes.
My iptables config was actually fine. I already had IP forwarding enabled too.
Found the solution in this post...
I have been battling trying to get something working for a while now. I'm close to just giving up as I just can't seem to make it work exactly how I want.
I am trying to set up iptables on an Ubuntu Server 20.04 LTS to accept traffic from the LAN and route through a VPN tunnel that is...