This is what I found out about DS Lite for my Virgin router
The reason why the port forwarding option is missing is because with DS-Lite, your IPv4 address is not actually routed to you. It is coming from a CGNAT device in the Virgin Media network, meaning it is shared across multiple VM customers, not just you. This makes port forwarding impossible, because the IPv4 address you have isn’t directly on your router, instead you go through a local IPv4 subnet which then is translated to an external IPv4 after going through their network
Might be worth contacting your ISP though as I actually had so little trouble I bought a lottery ticket believing myself bewitched with good luck.
.sjb