Hi, i have micro bore central heating system, has worked fine for some 15 years but....the plumber seems to dislike it, the manifold has 4 returns and feeds for 7 rads!! and since the system was drained and the plumber reduced the size of the manifold it refuses to work. He wants to change pipework for 15mm, and who will have to pay for this change? In his wisdom he has boxed in the manifold and drain valve, any ideas