Bigmuz7 - looks like my information is out of date. Some time ago I was given a tour of the Hammerite production facility at Pridhoe, up north. They boasted of the xylene recovery system - flipping expensive stuff to allow to escape and not good for the environment. They explained its "being I the same family" as toluene. I am not a chemist nor wish to pass myself off as one.
From what I can remember the best advise from them if there was a spillage or as in this case vandalism, don't delay trying to shift it. It can take weeks to cure fully but after 24hrs is already well on the way to permanent bonding.
Hope the OP has had some luck getting it off the tubes.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former --- Albert Einstein