Just a quick update on this, I've reverted back to using Virgin DHCP/DNS
Something screwy was happening with the DNS, everything worked fine apart from my PS4 was having issues sending game invites and getting DNS timeouts!!
No idea what was going on, but it appeared to be resolving and responding at the server end!
So back to looking for a hardware based solution for the moment, I'm fine for the VPN not to be on the router, but I need something that can act as a DNS to resolve local network names from DNS!
Ideas on a post card!