Recently our Thorn Apollo copper boiler (30/50) - 23 years old - had started making noises. The best I can describe is to say sounds like 'fluttering' just short of the banging which I know as 'kettling.' This builds up from none to noisy enough to be heard in other rooms than where it is located in the kitchen. In the early days we had banging and adding Fernox solved it - but over the years has probably become very dilute.

As we are covered by West Midlands Gas maintenance contract - I asked them to visit. The Gas Fitter/engineer said that it was due to a build up of solids on the heat exchanger and that it would need to be replaced. For this to happen the system would have to be drained down and on filling 500 ml of Fernox boiler noise silencer added, at the time it sounded logical. He said this is not covered under the contract and that I would have to pay. He left me a quote of £564.83 - this seems an awful lot of money. This does not include a system flush - and radiators are uniformly hot anyway.

If this work is considered necessary I aim to get a quote from an independent Central Heating company - though expect I will have to pay for them to come out and assess the situation anyway.

However since I made the call for the visit the noise has been getting less and was not at its worst when the engineer called. For the last 3 days there has been absolutely no unusual sound whatsoever. This leads me to think that his diagnosis may be incorrect.

I would be grateful for any views, suggestions.

Conrad