Tony this looks like mine was - big job but really rewarding when you start to break the back of itWell it all started with i will sort the grill out new thermal sensor order. Then i had a thought
If we get some caravan bord of a lighter colour instead of the dark brown it will make it lighter in hear OK says the boss so order 5 sheets arrive next day . Good say I will make a start started to take the old bord off Sh say's I its all wet behind here where it leakingView attachment 19187
Are you replacing the walls with ply?
Take a look at this - search eBay and type in “plywood substitute “ this is what I used and now if I get water (which I’m sure I won’t ) it won’t cause any problems is it’s a poly plastic so water has no effect
Just thought that might help