I cant find my original thread on here seeking advice but I finally managed to solve the long standing problem with my Mums central heating - ran a magnet over the pipework and discovered this -
Replaced the pipework and everything is working again!
It started with the system drawing in air/poor circulation, then when HW was selected most of the CH would stop working. I replaced the clogged pipework, then gave the system a blast with Fernox DS40 and it is running much better.
