An explanation of the the up to 8 Meg products click here
This click here explains how to set up your Sky router.
Using the link given, post back with the details on your routers status page and I'll try and figure out why your connection/speed is so slow. Depending on if/when you reply, I may not be able to answer for a few days but will chack back asap.
It's not your exchange that can go to 7 Meg, more likely that's the estimate for your line.