So I have looked into this a bit more, and read up on ALTQ etc. I understand now a bit more about how it works, and why you can only shape traffic the leaves an interface (because if you think about it once the traffic has entered the interface its already there and used up the bandwith).
What I would like to know though is if I have multiple VLANs assigned to the same physical interface, can I think add a queue to that interface and shape all the traffic across the multiple VLANs?
Regards
Ben