Hello Cricketbluebell,
This is always a problem and unfortunately the sun will eventually fade pretty much everything. However the best solutions I've found for amateur use are:
Use a permanent marker - I've noticed these in stationers in a large range of colours recently.
Buy a labelling machine from a stationers. You just type in the name on to adhesive plastic tape and stick it on your label. This lasts for a long time.
Use pencil - yes it works well. It's the method I was taught at horticutural college and has the advantage that you can erase your writing and re-use the label. Soft pencils work best.
Good luck!
Emma.
gardenersworld.com team