....much messing around later.
Changed the voxalot settings to go use the US server (was on EU). Forwarding to mobiles now works on both accounts. Actually switched off the ATA so this fowarding works without voxalot having my IP address to pass to betamax -as I'm not logged into voxalot. Is this right? Am I missing something? Is it because I am forwarding to a chargeable number that they don't need the IP address. Or maybe its cached somewhere and in an hour or two the forward will stop working!!
Steve