The sprung tensioner looked a bit of a pain, but the manual tensioner was straight forward.
Alternator was easy, just getting is out past AC pipes was tricky.
There was plenty of access once the wheel arch trim was off. This was on a 306 though, Berlingo might even have more space.
I only had a Haynes manual for reference.
Ive just had the same problem,Ive changed all the wheels and to no avail as the noise is coming from the alternator you can prove this by taking the belt off and running the engine,if the noise stops its the alternator[or the pump] but you say you changed yours. to take the belt off you need a long 15mm spanner and a home made tool, i used a flat piece of aluminium carpet strip 70 cm long, drill a hole at the end and put in a thin nut and bolt, the bolt protruding 2cm out from the nut.
Now push the tensioner back with the spanner and stick the bolt in the hole on the tensioner body, you have to wiggle it a bit to get it lined up, when its locked you can remove the belt.
Dont forget to draw a diagram of belt run and have fun.