Plumbing issue

[Arthurnewyorkcity]

I will start by saying I am useless at all things diy.
My house was built 1950s. I have no internal stopcock, just the one outside my property owned by the water company. I had central heating installed 2 years ago. No issues there.
My water supply goes up through the house then down again, bit of a backwards system.
My mains pipe sounds like someone is almost constantly hammering it after water has ran. This can last hours. I am going crazy. The pipe isn't loose that I can feel.
What can I do, if anything? I don't want to call out a plumber if it's an easy fix. My neighbours can hear it!

Well the first thing I'd do is get a plumber to come and put in a stop cock.
It sounds as if you have a cold storage tank high up in the property (usually the loft), fed by the rising main. The water hammer issue might be solved with a new washer for the ball valve - or maybe a new ball valve. But it might not. I would get a plumber to look at it as they have experience.

You can get a water hammer contraption that fits on the offending pipe. We’ve got one behind the bathroom sink.

I asked quite a few plumbers when i first moved in as I was worried over a potential flood and they all said not to worry as long as i can easily access the outdoor one and my pipe work is basically a straight mains running under front door to directly back of the house then spurring off so I'd need loads of stop cocks to isolate. There used to be one directly inside my front door (in the floor) the previous owners got rid of it as you couldn't lay flooring.
It doesn't sound like a leak at all? Sorry for my vagueness, i really am dim with all things plumbing etc.
I'll get a plumber out

What you are experiencing is called "water hammer". This usually happens when a valve is shut - could be a valve in a washing machine, a tap, valve of a water tank. The sudden closures creates a pressure wave, where the flowing water is suddenly stopped and, in effect, rebounds off the valve.

Many homes have an air chamber that absorbs this shock wave - over time this can fill with water, and inturn you experience water hammer.

If you have an air chamber, it can be emptied by turning off the water supply ( your external stop cock), and running a downstairs cold tap until the system is empty. Then close the tap then turn the stop cock back on.

I would try this before calling in a plumber. I'd you don't have a chamber, a plumber can fit one or fit an arrestor.

It doesn't sound like a leak at all?
No it's not a leak.

Thank you all for commenting! Really appreciated. 30 year old female doing my best to learn. I'll try your suggestions first thing tomorrow.
Thanks again!