Thank you. I'll look at the M-bus method, too.
In the meantime Elster have responded to my writing to them and have provided a 9 page document on the IrDA output of the Elster A100C meter which is used for many single phase applications. My application uses a three phase meter - the Elster A1100. In the e-mail the sender asked someone he copied to provide me with the same document for the A1100, if its output is different. I hope it is as I would like to be able to monitor each of the phases separately.