Belated thanks everyone for this advice, which I've followed as best I can.
The WiFi strength hovers between -47 and -51, so not ideal but still seems to implement any changes made on the NAS.
JFBUK thanks for your comprehensive guide. I've downloaded Picard and followed the steps, the only issue I'm having is with the scripting.
Under 'File Naming' and 'Edit script...', do I then need to create 'add a new script' then copy-and-paste your suggested script values, or add in other values, to make it work?
Sorry if this seems obvious and I've missed it, but this is where the gaps in my knowledge show.
Otherwise, I can follow the rest of the steps and load up compilation albums from the NAS etc, I just need to be able to identify and pick out the metadata tags I want to keep.
Any help you can give you to help clarify this would be much appreciated.
Thanks again in advance