To be honest, I had a bit of a bad experience with Waxoyl where it actually let water under it. I don't know it that was a one off thing or not - I have been considering these guys, as I used some Dinitrol myself in the sills and was quite pleased with the stuff. Only thing is, it takes two days and it would mean hiring a car to get home while they do it.
http://www.rust.co.uk/dinitrol-rust-...om-250/c32734/