I am going to install a new thermostatic shower mixer, this needs to be
fitted into a double skinned plasterboard wall. The skins are only
about 60mm apart, so I was thinking of creating a large-ish hole and
then filling it with a tiled piece of MDF. This would mean I can screw
the mixer to the MDF panel and just drill some large access holes in
the plasterboard from behind for the pipes to come through. ( the pipes
are in the airing cupboard behind the wall) Is MDF suitable for this
sort if thing ? Would i be better off using somthing else ?

Simon