Ask an Property Solicitor. Get an Answer ASAP.
You are responsible for any pipework and sewers on your own property.
Any foul drainage sewer on your neighbours property is classed as a public sewer and thus is the responsibility of Anglian Water, as this length of sewer is shared.
As regards ***** ***** supply pipe on your neighbour's property, this is your joint responsibility.
I hope this assists and if so, I would be grateful if you could rate my answer in the top right hand corner of your screen.