1997 Vauxhall Astra Drive belt replacement

My V-belt running the alternator, power steering, and air conditioning disintegrated (without warning) and I found a workshop who replaced it for me. BUT, I am getting constant noise from the belt and the alternator is not charging the battery properly because the belt is constantly slipping.
Another mechanic has told me that the belt is too small and has been installed incorrectly!
I need the routing diagram for the car so that I can go back to the original workshop to get them to fix this.
I have been searching the internet for this diagram, without success, and the workshop manual has very brief instructions but no diagrams.
Can you please assist in this regard?
With thanks
Ian Courtney