steering problem

Hi, can anybody advise me, earlier today I had new discs and pads placed on front of my G, at the same time my fan belt was a bit squeaky so asked my mechanic to replace it. On picking up the G he told me he replaced the power steering belt as well. Drove the car away everything fine brakes brilliant no more shudder and pulseing on the pedal, but the steering is very strange, on turning right its fine but on turning left it feels stiff and fails to return properly needing adjustment to get wheel straight again. Obviousley called mechanic and he told me to drop it down in morning, he thinks the power steering may need bleeding or adjusting. He,s a really nice guy and a friend for over 5 years he works on classic cars, and is porsche trained, just thought someone might be able to point him in the right direction.

regards Frannie