before u get a new pump...
have u checked the power steering fluid...
if you have then try this...
There is a rubber grommit up near the brake master cylinder... Get someone to turn the wheel side to side while u look under the bonnet, you will see the shaft (looks like a ROD) moving side to side, follow it up, until it dissapears, Thats where ur grommit is... Lube up that area, with some grease, or any type of lube. (its hard to get in there so the spray on lube's are good, or just use a screwdriver)
Now dont be scared to smuther the lube all round the grommit.. Once its smuthered turn the wheel side to side to get all the lube around the area...
Then see how u go...
Nothing to worrie bout, alot of commo's have that problem...
Trust me if you go to a mechanic they will say its the pump when it probably somethin as easy as lubing a grommit...
let us know how its goin...