Simon, these sort of pages are what makes the Web so fantastic. I've also been mucking around for hours on exactly the same problem, and this seems to be the only site that makes the problem & its solution clear. Thanks again!
More and more of my posts are taking the this form; I have a problem, I can't find the solution by googling, I eventually work out the solution, I blog it for the benefit of others who will google in the future.
I find it so gratifying when someone leaves a comment some months later to say that my post solved the same problem they were having. Firstly, I'm glad that I have actually saved a few hours of somebody's time, and secondly, I get to feel all nice and fluffy and warm inside.