another noisy thorn boiler

Hi, our home has a rather ancient looking wall-mounted thorn olympic 38/50b boiler. The radiators work well and are mostly in good condition externally; but over time the boiler has progressively got noisier (intermittent knocking noises) which are quite loud in the garden and noisy in the upstairs bedrooms. Apart from the noise the boiler works well and delivers good heating and hot water. I have been 'warned' by British Gas central heating care that (i) we need to be aware that the manufacturer has stopped making some of the spare parts and (ii) that we should consider replacing the central heating system or (iii) when pushed British Gas said that we could just replace the boiler which may be scaled up - apparently the whole system would need to be flushed out (assumably to get rid of scale?). Seemed pretty wasteful & undoubtly it will be expensive to replace a working system (apart from the loud noises) but do not wish to be caught short with a system breakdown during a cold winter. Your advice much appreciated ? regards Patrice

seems like good advic but the powerflush is to remove sludged up water not scaled up water

DOes this particular model have the high/Low switch? If it's OK on Low, leave it there.
If not, turn the boiler stat down.
You could try using something like a fairly gentle Boiler Silencer, Boiler Descaler or System Desludger/Restorer chemical, which you'd circulate for a while and in most cases have to drain/flush out.