Power steering noise on Ford Focus, still works?

Suddenly, my power steering has got noisy. It makes a noise when idling and increases when I press the gas pedal and also when I turn the wheel. The power steering fluid level looks OK, a little bit below the minimum level but I can see it when I take the cap off. Is this just going to be a quick belt replacement or something far more expensive? Is it safe to keep driving? And also, can The AA or RAC fix this at the roadside or is it a garage job?

The pump is likely broken. Have a mechanic look at it.

Pump is shot, time for a new one.

Just had the RAC out, I've got a fluid leak. The level was only just below the minimum but enough to cause the noise. He topped it up and the noise has gone. The leak isn't obvious, he had a good look and could see the tray below was wet. He suspects it could be the hose and not the pump but at least it's given me a bit a breathing space to get it booked it.