It seems the A1100 does an aggregate total only, so you will not be surprised.. 
Elster e-mailed and advised this.
I also wrote to Landis&Gyr/Ampy and got a rather useless reply - 'we don't support the people who buy our meters unless they're a massive conglomerate so you won't get that information from us' - I paraphrase, of course. Elster were much more helpful.
I'm still sourcing parts but will come back with any further news when I have it.