Taking out the U-bend sounds like the most plausible solution. I don't like pouring dangerous chemicals down the drain unless I really have to. Unfortunately Mr Skweeky is not blessed with any plumbing skills. Her Majesty's Forces tought him how to fix helicopters and shoot people and that's it.
I shall have to call in Mr Skweeky's best friend. An IT consultant with a knowledge of plumbing :yes:
