Much easier than I expected
I bought the vinyl from Tunnel Vision and downloaded the visual from lovesvg.com before adding the personalised text on the ScanNCut. I then flipped the virtual visual to give a mirror image and put the vinyl shiny side (ie carrier side) down on the cutting mat before cutting with blade 4 and pressure 1.
the excess vinyl was peeled off the carrier and the remainder (the vinyl I wanted) placed dull side down on the T-shirt (peacocks) and ironed to fix it. Once cooled the carrier sheet peels off leaving just the image in place.
now, what else can I cover in vinyl?