Thanks for the pics and the quick reply! It looks like I need to switch one of the front spacers and I think i have lost one of the side spacers!
I guess people already know, but I found that removing the sides is best for initial access, then once these are steadied out of the way, undo the front from the top to allow bar removal. Then when working to put the belts back on I found that working from the rear left hand side towards the front right hand side gave the best order for reinstallation. You need to slacken the grub screws on one side of each bar to allow the belts to find their own centres before levelling each side up and retightening the grub screws.
Only the front bar holder had worn, which is a little strange, but i replaced both front and rear as I dont fancy doing the job twice!
Think I will print myself another spacer before I strip it again.