Hot water pipes clanging when hot water turned on/off

UnsureAboutthis

Just worked out the white bottle is a 'condensing trap' bottle
do all boiler services inc the cleaning of that?

UnsureAboutthis

ok, just worked out where the inlet water allen key nuts are to turn water off to boiler
I will turn off boiler at mains first

I will then see if still get a hammering sound

ThisIsWeird

Cleaning out the condensate trap is usually very simple, and is worth doing now and then - mine actually filled up with debris a couple of years back, and started to dribble out the cap!

UnsureAboutthis

Thanks @ThisIsWeird

UnsureAboutthis

update
We've had the plumber around today. The first was visiting next door yesterday. I told him what I have done and my concerns and demonstrated the water hammer and then how it does not happen, ie turn on another tap before bath hot tap. He was lost and suggested an Arrestor but was not sure where to fit it, IE near the stopcock or another place
I've contact several plumbers, many don't respond or just give a quote over the email and I'm not convinced quotes var from 150 to 300.
I invited one to visit today he came around 7pm - he was honest and unsure but suggested an Arrestor - I asked him were to fit, he was unsure but agreed with my that very neat within 2 feet of Stopcock. 

I think we will try an Arrestor, but the unit backing needs cutting out and it hurts as the kitch looks new and thick back boards and I will cut it away - plumber was saying its an hours work 80 quid plus labour - he seemed genuine. I'm aware it may not work but plumber never said that

I am going to sleep on it as most of the massive noise is turning on the bath hot tap. I've changed the interanls of this bath tap between the cold to hot and hot to clod, no difference

Any further suggestions? I will give the Arrestor a go - the one on screwfix with around 500 feedback and 4 star average reviews - unless you guys can think of a better one