2000 GU ST4500 Petrol Auto - Air Compressor V belt replacement help please

Hi all, I am in the process of replacing all 4 V belts as 2 needed to be replaced so figured best to do them all now.

I am having trouble with the Air Compressor belt getting it back on. I have removed the idler pully to try and assist but still not able to get it on. I have checked the length and they are the same, but not the same number despite checking correct vehicle via number and VIN plate when ordered from Supercheap, if anything the new one is slightly thicker, maybe a 1mm more.

I have the power steering undone and pushed to the side so I have pretty good access. Fan is removed, however I have not removed the radiator shroud or any water pipes as I would prefer not to.

Is there a trick to get this on so I can then add the idler pully back on and tension accordingly? Does the Air Compressor have an adjustment or loosen bolt to move it that I have not yet seen?

Thanks