Having read this back to myself I do seem rather curmudgeonly, don't I!
Not at all BC, i think this is an area we all agree on.
The UC loos (and really, any UC feature, such as the bar) are for UC passengers , and should be for their use only.
I have no issue with an UC passenger quietly asking the FSMs/FAs permission to bring a friend from W or Y up to the bar for a drink, i dont think many of us do, but it is not fair for W and Y passengers to avail themselves of the bar/loos at free will. Its not being curmudgeonly, its ensuring that UC passengers are getting what they have paid for and not diluting the brand.
I think the BS 'rope' idea is a fine one, and would be happy to see it myself. A lot of other airlines are verry strict on stopping non premium passengers from entering their First & Business cabins, so i think VS need to follow suit here, and not just on ex-LHR flights. LGW UC should be treated the same as LHR UC.