Sky Broadband have a Fair Usage Policy...maybe that accounts for your slow speeds
Sky.com - Usage Policies

Try downloading a file from here & see what speed you get. Slow download from this site often points to an ISP throttling bandwidth.
+ MagnetMix.com +: The Source for Good Content

Try changing ports (no guarantees but it's easy enough to try). In LW tools > options > advanced > firewall config. Change LW's listening port to 64049, or something in the range of 49152 - 65535. Click on Apply to save the change. If you have specific ports allowed through a software firewall, or a port forwarded within a modem/router, these will also have to change!

If you give us your system details, we might be able to help more!
System details - help us to help you (click here)