Ok, I've also found this thread
https://vborg.vbsupport.ru/showthread.php?t=96057 where one of the moderators has stated that this could easily be made into a plugin for it to be made to work again.
I've tried the obvious in copying the code to a new plugin and trying to make it as a bb-code parse plugin, but I get the white screen of death. I'm not quite up on the new vBulletin variables and stuff yet so aint got a clue if the code actually needs updating and stuff or not?
I really would appreciate a hand with this one, it's got me seriously baffled.
It's probably something really simple and straight forward to do, but I think i've probably spent so long staring trying to find the answer that i'm suffering from a problem black out.
Anyway, thanks in advance if you do decide in your heart, that I am worthy of being given a wee helping hand on this one. I promise that if I can at some stage in the future help you back out in some shape or form, I will.