@mitu All sorted now thanks.

I ve managed to do it through some commands. Thanks anyway! :)

Found the culprit. Please use Option 1 in the above mentioned wiki to include the roms from your NAS. Then it's working. It will not work with Option 2. Thanks. Leaving this for others, if they happen to get into the same issues.

Perfect, thanks for the replies! Another quick question, I can mount ext drives on my Mac, so I can edit files on the main retropie partition, with this in mind, is there anyway I can manually replace / edit scraped data? Some of the games I have scraped have the incorrect pictures or can't find data at all, so I would like to manually create / edit some of them. Is this possible, and if so, where are the files? Stewart

@enderandrew This isn't necessarily the case because some USB 2.0 flash drives are a lot slower than what the USB 2.0 standard allows in my experience. With A USB 3.0 flash drive, you will likely see performance much closer to the maximum USB 2.0 is capable of on the Pi as they are built for speed. I bought a low-profile USB 3.0 drive for this reason and in my case, throughput did not disappoint.