There are other options for short run full colour prints, but as with most things, each has it's pros and cons
White/pastel t-shirt transfers - Cheap, very good image reproduction and offer a fairly nice finish, but any white areas left on the design do leave an off white appearance on the t-shirt due to the transfer adhesive. A4 & A3 available.
Dark clothing transfers - Offer the option to be cut with a vinyl plotter, but sit on the fabric rather than bonding to it. Finish can feel quite thick and plastic-like. A4 & A3 available (unless anyone has a large format printer
)
High-end transfers - Suitable for dark and light colours and are 'self-weeding'. Gives a great finish and is described as having a finish very close to screen printed tops. Process is quite involved (unless you have one of the new white toner ink printers) and the cost per print is quite high (£3-5 more than a vinyl cut t-shirt). A4 available.