Sorry progress has been slow but finally stripped out the old sink & cabinet and also part of the inner rear wall . Still some behind the wardrobe and shower/bath but the bath side appears fine .As the wardrobe is all rotten at the bottom due to leaks thats being replaced so its find out what the rest of the wall is like.
Now for the wall I have investigated...
not good. The rear wall appears to have been constructed out of plywood sandwiching styrofoam insulation pieces and horizontal metal box tubing ,with wood & metal box cross bracing.
Metal is well rusty but not rusted through, plywood either side is totally rotten/black & wet
. Peeling off the rotten wood,removing the insulation can see the reverse side of the outside fiberglass/gel coat ! luckily thats in good condition . So plan is to gut all the rotten wood rustproof the metal tubing and get some more modern insulation.
Pictures to follow.