I've now run a the Electric Cable for the Van into the house so I can run the Fan Heaters from the sockets in there and have purchased a second fan heater to help dry the van out.
The rear area of the van where I reboarded the original 'damp area' is now reading damp again... this is down to a) not drying the area out fully before (I didn't have a Damp meter when I undertook this work and couldn't check the Spar - even though it felt dry to the touch it won't have dried completely) & b) Water travelling back down the Spar from behind the bathroom and wardrobe/cupboard areas.
So I have now removed the Rear Cupboards above the back window.... by unscrewing the fixing screws and droping the cupboard down the wall onto the bunk bed holders.
The wallpanel is then scored again and the original repaired panel is removed with the wallpaper scraper again as with the other areas already stripped. Using the Damp meter I work out that the original 'damp' area had gone further down the wall as I get a yellow warning on the Meter. So I have taken this area out too.
So the entire van is stripped from front to back along the wall - I have two Fan Heaters running and the batons/spar is SLOWLY drying out but it does seem solid enough so I'm hoping that I can apply a coat of wood hardener and not have to open the van side up to replace the wood......