Power Steering issue

Hi, a couple of weeks ago I had the power steering pump replaced in my vehicle. The car was making a grinding noise when the wheel was turned. It cost £600.

I got it back and it was okay for a day, but then the grinding noise slowly started to come back. I took it back and have now been told there is a leak in the power steering rack and been quoted £700.

From my point of view, I would say that the power steering rack was faulty from the beginning, and it was missed during the original inspection - but he is suggesting it is a separate fault and that I can't get my money back for the original repair. I find it really hard to believe that a separate issue with the power steering occurred a day later. I'm just wondering how likely is this?