Hi everyone, I've had the Alternator & Power Steering Drive Belts changed in my Defender 200 tdi and after driving back from the garage, there's a loud squeaking noise coming from under the bonnet. There's no squeak when I've got the clutch down and the squeak gets louder/faster in higher revs. Phoned garage and apparently no one available to help/advise.

Any advice on what to do?

To check it's not the belts, with the engine running spray the pulleys and belt with WD40.
Rev the engine, if the squeak goes (or doesn't appear) it's not them.

Start the engine, put the transfer box (LT230) into neutral and engage 3rd gear.
Listen for the noise closely and see if you can pinpoint where it's coming from.
Try this in all gears.

If you can remove the drive/prop shafts (you will need a 9/16" spanner or a 'good' 14mm)
Start the engine, put the transfer box (LT230) into high and engage 3rd gear.
Listen for the noise closely and see if you can pinpoint where it's coming from.
Try this in all gears.

Let us know how you get on

Are you sure it’s not new belts on old pulleys?

Water pump bearings?