Good evening, I highly suggest you get the correct entried by using ADSIEDIT -finding the relevant object, right click > properties > go to the value named DistinguishedName and copying this
This will give you the exact OU path to use for mapping.
ADSIEDIT can be run by using adsiedit.msc from the run prompt but you may need to install it, I believe this is a freely available tool for download if you don't have it
Thanks very much for this tip
Im going to be working more on the script today in work. Will let you know the outcome.