Really the best way to handle this is to return all the data you need in one dataset as it reduces round trips and makes working with the data in SSRS MUCH easier. That being said I have done this, but it has been awhile, so I may not get it all exactly right the first time.

First you need to create your table with the invoice details dataset, do not use a details row, put everything in groups. Then within your innermost grouping place a table for the meter information records. I believe you will need to put a filter on the meter information table to link it to the parent table.

If I have a chance later I will try to put together an example report using AdventureWorks so you can see what I mean.