Removing corrupt files that didn't sync properly ('Other' space)

iPhone 6 / 128GB / iOS8

Whilst I was setting up my new iPhone, I was transferring my music across (8,000 songs) and I accidentally knocked the USB lead out at around the 6,000 song mark - very frustrating. Therefore the sync stopped abruptly and failed to complete.

I re-synced the next day and all my music transferred successfully (taking up around 46GB in space).

However, iTunes now displays that I have around 35GB of 'Other' space on my phone. I've searched online and it seems that this space could be the corrupted files from the failed sync the day before. Is that correct? 35GB is a huge amount of space for 'Other' and clearly can't be the usual app data, messages, etc, so this seems to make sense.

Is there a way to remove these presumably corrupted music files to free up that 35GB of space? Reluctant to restore the phone but if it's the only way then I'll have to. If I do restore, will it just re-sync those corrupted files and put them back on the phone (or does wiping it fix that issue)?

On another note, transferring my music (8,000 songs) took 12 hours! That doesn't strike me as normal - should it really take that long? My laptop is fairly new, no real issues with it, and obviously it's a brand new iPhone so I'm surprised it took that long - and was concerned at leaving my phone plugged in to charge for quite so long two days in a row.

Any help is much appreciated!