Ring 105 from a land line (you can call from a mobile but it won’t put you straight through to the right people as it won’t know where you are) and it will put you through to your distribution network operator (dno). They are the people who look after the cable running up to your house.
Next time it happens, check your meter. If that’s still on/turning while you’re off, it’s likely a problem on your side. If the meter is off as well, it’s the dno.
The more information you can give, the quicker they’ll resolve it and report it every time it happens, they’re not psychic. They may try and class it as a quality of supply job. These are when lights just flicker a bit. What you’re experiencing is an intermittent fault. The key thing here is that things don’t flicker, they go off.
As mentioned above, it could be every third house if it’s one phase on the main. If the street light is out at the same time but everyone else is okay you could both share the same service joint. It could be that the lamp service has blown off and that’s causing your issue.
Tell them how close the lamp is to your house. When you and the lamp are off, but when you come back on. Tell them if anyone else is affected. What times it happens, is there a pattern, what the weather is doing, is there a common cause.
The call taker won’t care about any of these things but the engineer who gets the job will.
You might end up waiting until it goes permanent. Those sorts of faults are much easier to find!