Well, went to van today and there is an awning rail inside loo compartment. So that's figured that out. It is indeed a shower curtain!
I'm thinking that these washrooms were designed when people were smaller than today. I might have been ok in the 1970s but 40 odd years of lifestyle has taken its toll.
And certainly, keeping things down to a reasonable level of decibels is going to be challenging with such flimsy soundproofing!!!