On another note, one of the ISPs i mentioned on the previous page, unchained, are now offering a 1gb line for £1 a month more than Zen and are guaranteeing a BT Wholesale backhaul and I think they have all of the features that you are looking for - so you might want to keep that information in your 'back pocket' in case it all goes pear shaped with Zen again.
Thanks for this pointer. I had a look at Unchained and they look very interesting, they can do slightly off the beaten track things link do you a block of 8 static IPs for £6 a month, and a real person answered my queries over the weekend, so I'm going to give them a crack - as I'm out of contract on AAISP and getting a bit fed up of moving my connection back and forth between 1TB and 10TB to try and save pennies. I've asked to have an extra provision put in (instead of migrating the working AAISP setup) - so hopefully will get a 4 port ONT, and will then cease the AAISP line once I'm happy with it.