I have a 05 GT Jtd with 18 inch alloys that just came with the gunk kit - I bought a space saver spare from alfa that fits in the wheel well and a jack from halfords.
Just as well I did because about a week later I burst my front tyre in a pothole and no amount of gunk would have filled the split in the tyre.
My view is tins of gunk are a waste of time - they can't always fix a puncture and you don't always get a puncture when tyre shops are open or nearby
I forgot to say you would need to get a wheel brace too as this isn't included either
old post revisited. What type of jack did you buy????