When I showed a picture of my Garden Rail Mostyn 7 van, someone asked me where I'd got some GR transfers from. I explained they were a print-your-own waterslide set but couldn't find the details.
I've used the same stuff for the shipping container, and have tracked down the supplier:
I use the clear background version. Simply run them through the inkjet printer, spray with a few coats of satin varnish, leave to dry and then use as normal. Microsol and Microset seem to work on them to make the sheet, which is a bit stiffer then "proper" transfers, bend over lumpy bits of the model.
They work well for this sort of job, but if I'm honest, the Humbrol varnish makes them slightly yellow, and you need to put them on a white background as of course, the printer doesn't print white. Maybe I could use a different, or just less, varnish.
Basically, if Fox Transfers do something suitable - use that. If not, this will work, but isn't as good.