For any UK seller who's got bored fighting with the Royal Mail price finder, I rolled it all into one at http://213.143.2.53/postCalc.php

Go ahead and help yourself if it's of any use to you. It's tailored for my own needs so ignore the packaging costs if you just need a quick service cost by weight. A time saver as it gets the International prices without having to do repeat lookups. I checked it pretty carefully but if you find any errors let me know.