How to plasterboard half hollow wall with gas pipe running up it

I recently had a breast wall plasterboarded and skimmed, however the right side cheek of the wall wasn't done because of what was behind it. That wall has concrete on the left, hollow in the middle and on the right there is a big gas pipe running from bottom to top!

This will be easier to understand with pictures:

I'm not really sure the best way to approach it, the plasterer who did the rest of the wall suggested some wooden battens running horizontally across the wall with the plasterboard stuck to them, the problem then will be there will be a gap between the external corner of the wall and the new plasterboard.

The final complication is that there is a valve sticking out the case pipe towards the bottom, so I would probably need to box this out of the plasterboard.

Anybody got any suggestions? Ideally looking for the simplest solution but i know in this case there probably isn't one!

Thanks in advance.