If there was a rat in the attic what noises might be heard?  The noises then go quiet about 2 weeks then start anew Can this be explained?

Usually rats prefer lower spaces, although they're capable of climbing quite well. If you have an animal infestation in the attic but long periods of silence, you can presume that the animal, whatever it is, can come and go at will.

It's more likely to be squirrels, mice, or even raccoons.

The noises you hear are those of the animal moving around, making itself at home by eating what it can find or carry in, then rearranging your insulation to make itself a cozy spot to sleep. You won't hear vocal noises, usually.

You need to do what it takes to drive them out, then seal all the ways they're getting in. It's important to do it soon, before they nest and have babies where they feel safe.

My preference would be to hire an exterminator.

My question. I hear a very loud squeak. Another squeak a few minutes later, and this might happen 10 times, but then it is silent and noise is never heard at night. There are no moving about noises

And then it all goes quiet for about 2 weeks and starts again.

Only ever squeaks. If it was birds I would see them on nearby roofs. They always check before entering.

I don’t allow birds now. I suspect a rat.

No raccoons. I am in the UK.

its probably some fat rat in ur attic, or its a demon idk

maybe they left and came back