I was able to find workaround, but a "better" answer would be appreciated.
I saved the labels as a workspace variable called 'data.mat' (the label was 'data') which I then saved using the command window via:
save('data.mat','data','-v7.3')
This isn't ideal as my data sizes run up agaisnt the RAM of my machine, and adding extra variables to my workspace is to be avoided (why I am saving as .mat files in the first place).