Phew!

I am wam again. although 00 my not look like a good result it is 110%  better than fault L2. L2 = no heat or hot water. 00 means that all is working and, indeed, up to temperature. According to the nice chap from British Gas it was a blocked something or other. Not, at least in theory something that I could have solved. However....... I watched very closely. Hopefully there won't be a repeat.