Power steering problem-- Help!

[elvera]

My 2003 2.8 hdi boxer had cambelt and bits and waterpump replaced a year ago as due; done by trusted garage. A month or so later on start up there is a clattering noise if the steering wheel is moved even slightly to the left or right. If the engine is warmed up beforehand there is no noise. It has been back to the garage twice. Inspection of wheel bearings ball joints etc - all are OK. And of course by the time I get there the noise has stopped !
I have been informed from another source that the problem might be that :- "when the cambelt was replace the small spacer that goes between the engine and the cover has been fitted the wrong way or not properly into the recess where it should sit. A new cover will be required, as the belt will have worn it -etc"
I have ordered from localish Peugeot the parts 320V3, 320V4, 320V5. which I am told are the small spacer and two covers, just to be sure. Should have them in a couple of days when my garage will attempt to mend.
Can anybody help with a possible cause and the parts & method to fix? Thanks.