cheers for the help guys. I managed to take the plastic "bush" thing out and it was cracked. ive glued it together and ill see how I go. since then ive done a bit of research and part numbers are PL08 for the bottom tube or PL09 for the top tube. if it breaks again ill just replace.
I never do the wing nuts up tight, just enough to stop them moving so I knew it wasn't the wing nut that had stripped the threads.
was hard for me to find as I didn't know what they were called.
this is it here, the black thing.
@Zickos - its very common in the UK to let support acts use your shells. im quite generous/lazy and I let people use my hardware too unless they are being a bit rough with it. ive never had anything fail on me before in the 10 years ive been gigging, so I cant complain.