Obviously I will have to cut out a long section of plasterboard.
Before I continue with this route has anyone got any better ideas.

It's definitely the way I'd do it. Make the wooden battens vertical, as it
would be stronger than horizontal battens or isolated pads.

To attach the wood to the blocks, use meaty screws (i.e. 6mm x 75mm) and
brown plugs. Alternatively, use rawlbolts.

The other alternative is to cut back the plasterboard all around the wall
units and mount the wall units directly onto the concrete block. Then patch
the plaster. This leaves the units embedded in the wall somewhat.

Christian.