Wet & Wild take some beating for service!!
Used them for the past 5 years or so and exceptional speed and shipping over here to California.
http://www.wild-graphics.co.uk/wild2005/about.php
Email them for quote and ask for flexi-vinyl lettering.
Is ready spaced and self adhesive.
The small reg letters have been on my RIB for 5 years and just about need replacing. The larger "bayshots lettering" tends to last about 3 years,but I am out every weekend.
The hot weather here tends to exagerate the expanding and cooling,but the letters keep their grip.
cheers Dal