Ok - so I have got some way to sorting out problem.
Thames Water have been and it is not them
Got a man in and he has been here for the last hour and a half with his young apprentice sidekick.
They have to dig up outside the front as after ruling everything else out, taking apart my kitchen sink unit
, they have concluded the problem is from the inlet or waste pipe outside . As I said originally.
They are needing to return with a groundwork crew.
Meanwhile .....I think I have a new 'friend '