Quote (from the Sky website):
"What happens if I exceed my usage allowance?
Don't worry if you go over your allowance a little bit, we won't cut you off or charge you extra. You'll only hear from us if you're much more active on the Internet every day, and frequently/constantly uploading/downloading - then we may get in touch to suggest you upgrade to Sky Broadband Mid or Max if they will suit you better".
I don't use Limewire but I am aware that many peer-to-peer applications are configured to offer the best download speeds to users who maximise the number of files that can be uploaded from their own computer. If you're only 'taking', and not 'giving' at the same time, it could explain why you're getting poorer download speeds. (Of course, 'downloading' copyright material normally only breaches civil laws. i.e. you can be sued but not prosecuted. Making files available for 'uploading', to other people's PCs, is a criminal offence. If you let loads of people access files on your computer you might increase your download speeds but you also increase the risk of a criminal prosecution).
Chris