Thanks for the replies.
Managed to measure the pipework and needed to add another 3kg. Original charge was incorrect from date of installation by the look of it. System appears to be working ok now.

As I said though, I'm a bit rusty on these, especially these heat recovery ones.
Another couple of questions if I may:

1. I set all indoor units to cooling, yet one of the outdoors had a nice hot condenser and good heat rejection. The slave however, had the fan running full tilt and the condenser was cold, as was the air off. Why would this be if every system was in cooling, IE none looking for heat?

2. Can I assume the room temp is controlled by the board looking at the return air temp in relation to the controller set point? Ie, the larger the difference the more it will open the eev?

3. In a couple of the rooms, the return air was 21c, the room was at 21, but the room temp according to the wall controller display was 24? Is there a field setting to offset the readout on the wall controller so it reads correct?

Cheers guys.