I think this is probably fairly straight forward but I can't find any example configs.
I'm looking to set my cisco 877 router to pass all http & FTP traffic onto another bradband router to reduce the loading on this broadband line. Is this easy to do? If so could someone give me some pointers?
What you describe is fairly easy to do using the feature of Policy Based Routing. This link has information about how to configure PBR and should help you to get started with it: