I think you were right on Alan (OMG MICHIGAN WOOOOOOOOO).
I take it that you're from the UK s8n (feeling evil are we?). Anyway, no, using an 8m run with the proper cables will not harm anything. The only thing you run the risk of is signal loss, but with good stuff, it shouldn't be an issue. There are a few places online that will custom make cables for your application and length out of top-quality cable, but I don't know what your budget is, nor do I know what the international shipping rates would be like.