Go to micro-mark.com. They sell decal printer paper you can run through your inkjet or laser printer. You can either print on a white background or clear. Problem is you can't print white. But they work well and are not expensive. You just need to have good art to print off your computer. I've used them on professional models I made for Volkswagen, and they worked out very well.
I know that place. AFAIK they don't offer a wet or dry transfer (decal in U.S parlance) making service, but supply vinyl lettering, which sit proud of the surface (e.g a sticker). Now this may or may not be acceptable to you.