I've created a Live USB of Ubuntu 18.04.2, and used mkusb to do so that I would have more than 4GB of persistent storage. The process I followed is the same as this article.
I'd like to rename the partition names (currently casper-rw for the Live install and usbdata for the 'shared' partition) but am uncertain if this will cause any problems or break the system.
I will admit to not being well versed in Linux so I do apologise if I missed out any important information or something obvious on other questions which would answer this. Thanks for your help.