The Wilflex adhesive is excellent for shirts, but completely useless for mugs (particularly if you are going to do them in an oven as opposed to a mug press). The adhesive burns off quickly and the paper starts falling off the mug.
You must use a good quality heat tape (we buy ours from Cactus in the US) and put the paper on tightly.
If you're using mug wraps, set the oven to 200C / 400F. Make sure both the top and bottom elements are on, and put the mug in the middle of the oven on a baking tray, UPSIDE DOWN.
An oven with a thermofan is highly recommended. If you use enough heat tape, and the picture is tight enough, you can even dispense with the mug wraps, and make the mug without a wrap (this is what we use for metal wine bottle holders, vases and other items for which there are no wraps).
