Boulter Compact?

My boiler makes thumping noises when lit. It sounds like the boiler is about to fly off the wall. The thumping noise, dependant on which part of the system (hot water, radiators or underfloor heating) varies from a thump to a metallic type noise. I've had the boiler regularly serviced and the engineer has put some solution in to stop what he believes is kettling but still it makes a noise. The next suggestion is to have the system flushed. Has anybody else suffering the same and what was the solution. I'm told the boiler is about 7 years old. This noisiness only started a few months ago and is becoming quite unsettling as well as disturbing. Boiler is situated in the garage next to a spare bedroom and underneath our lounge. Advice would be much appreciated. Thank you.