I've finally figured with a Draytek router you can use a combination of Nat and no NAT. I have one external ip address allocated to the general network and then you can also us 5 of the other external ip addresses by setting up a different sub net on the router. I have all of my gadgets on internal addresses and two machines with different external addresses.
Maybe it was just me who's always wondered how to make use of the block off addresses that Zen provide. If anyone else is interested I will gladly post instructions as to what I did.
Freeserve Dial-Up --> BTopenworld --> <n>ildram -->Talk Talk LLU --> ZeN