I had a similar problem, and though at first it was the PAS pump, took it to the garage to check it over, they said the belt was fine put it back on etc and the squeek went, I think the tension had gone although saying that i did check the tension and all seem in order. Now my steering has gotten worse again squeek has come back and very heavy some times near impossible to turn the wheel when stationary and making a right old racket!
Ive got a replacement pump to fit, and going to check the current tension on the existing one, from what the haynes manual says its a few bolts that need adjusting? well on the diagram thats what it looks like