Banging noises in pipework

Hi. I have moved into a house that has a Boilermate 2000 running with an Ideal Classic boiler and we are regularly getting woken in the early hours by loud banging sounds coming from the pipes. It also happens when you use hot water first thing in the morning before the room thermostat has been turned up to make the central heating come on.
The sound is not coming from the boiler but seems to be somewhere in the pipework.
Both units were in the house from new and are now approaching 11 years old.
All the radiators warm up when the heating comes on with no sounds so I don't think it is air in that part of the system.
We have had a heating engineer in last week and he has put cleaner into the system 5 days ago, but it hasn't made a difference yet. He has said he will drain and refill the system in about a month.
The issue does occur at other times and seems to be related to the heating of water.
Are you able to suggest what the issue may be?

Sludge in system
Boiler pipes to unit may be blocked.
Check the unit takes water from the F & E tank.
Also that vent on BM 2000 is clear.
Boiler pump on Bm 2000.
Mike

Hi,
We have now had the left hand pump of the three on the Boilermate replaced, the heating system cleaned, flushed and drained/refilled (not a power flush) and that worked for about three days, but the noise returned and  persisted so the plumber came back last week and has flushed the boiler itself after isolating it from the rest of the system. Whilst it is true to say the noise is greatly improved now the pipes still have a slight banging sound to them when the water only is heating.
The noise seems to emanate from the boiler itself and is amplified by the pipes.
As part of the last process the flow/return temperature differential has been monitored at the time the banging was happening and it was within the limits expected.
Do you have any other suggestions as to what can cure it without junking it, as we can't afford to replace the whole system?!
Thanks again for the previous advice.

It is hard ref the noise.
It could be that the right hand side of the BM 2000 has a blockage.
Or is it the boiler making the noise due to scale in the heat exchanger?
If so boiler silencer could / would help that.
But again you have to consider the volume.
It does work though! A noisy banging boiler can go quiet in hours / days.
Mike

Hi Mike.
I really appreciate your help. If it was the heat exchanger would that make the water temperature fluctuate, as it doesn't and is always hot?
As I type, the noise is here again and is definitely coming from the boiler, but being amplified by the pipes. The noise is best described as a hollow echoing sound similar to when a kettle starts to boil. It isn't as loud as it was but is definitely intrusive in the early hours when the BM decides to heat the water!

The noise you describe is "kettling"
Boiler silence added to the system should stop that.
Unless it is something else.
1 bottle to every 100 litres.
The unit if 125 litre would be 1 .25 bottles. Or if a 200 litres would be 2 bottles.
The add a bottle for every 10 rads.
Always go over NOT under!
Mike

I'm very grateful for the advice again!!