The plumber came back on Saturday & removed another 2 feet of the pipe & it now seems OK. He told me to claim on my buildings insurance & say that he'd originally been called to fix a leak in the lead pipe (rather than to fit a new tank) and that repair had caused the bigger leak. He didn't give me a bill on Saturday but said to wait & see how I get on with the insurance.
I'm not sure if he's just done a lousy job & is trying to get a juicy insurance check or if it's just tough luck for me as it was a very old pipe? Any advice as to what's normal / fair / legal would be appreciated.