When I first bought the van it squealed like a stuck pig when the AC engaged which scared the life out of me on the drive home!
Initially I re-tensioned the existing belt, which cured it at low revs. However when driving around it would squeal again as the electro clutch kicked in with the engine at higher rpm or when pulling away.
Quick test to diagnose this is to turn off AC, drive around a bit and see if the noise stops
If it does, then with the passenger seat up so you can see the AC compressor, rev the engine and switch on the AC. It becomes pretty obvious where the noise is coming from and you'll also see the compressor pulley juddering.
I ended up changing the belt, which solved the problem. It's a really simple job. Once off I could see the old belt had chunks out of the teeth.
One thing I found is you have to tighten the pulley assembly bolt up pretty tightly or you lose belt tension again and the pig returns!
Worth checking the alternator belt as well.
If it's neither of these, next candidate would be the water pump. Luckily these are easy and cheap to get sorted.
Don't sorry, the 2L engines are pretty bomb proof. Very likely it's just one of the above and nothing major.