Hello @danwillis,
You may like to look at this previous thread, there are also many other examples here in the forum, just search on the topics of VLAN and Firewall.
The Peplink community works with a lot Balance ONE routers and with the higher end Balance routers (pluss the other gateways that Peplink make like MAX series). Enabling inter VLAN routing and setting up IP firewalls between the VLANs is the best way with Peplink, you will find the way Peplink do this better than the traditional routing tables (took us a while to come round to this way, though happy we have).
Happy to Help,
Marcus 