I've not done a 2.2 HDi, (yet), but it looks the same as the 2.0.....
I assume you have checked for play in the water pump, idler(11) and tensioner(9) pulleys?
If you undid the camshaft pulley adjusting screws, (3), did you definetly tighten them back up?
I guess you'd have to have the aux belt pulley off the crankshaft - could any of those bits have gone back unevenly?
Suppose a dodgy belt is not impossible either.
I got a mechanic to change the belt on my previous HDi and it whined noticably afterwards. After several rows over it, I just changed it again myself, (i think properly). I didn't have the fancy gauge to check the tension with, but our resident expert, jasper5, recommends seting it so you can just about turn the idler pulley without the belt moving. Remember to rotate the engine by hans a few times after adjusting, then re-check the tension.
HTH - Please let us know how you get on.