Although the unicom lines might be business, there is no reason why you shouldn't get a residential line from BT and get ADSL on that, although you would have to pay installation costs for the additional line.
Unfortunately i think the above is out of the question too, we're 4 miles from the nearest exchange i think so having a new line installed would be difficult, i think thats why the 2nd line we have at the moment is multiplexed into the original line.
The current line used to be a BT line btw, just that line rental is paid to unicom. I suppose i'll just need to wait until september when i go back to uni for broadband.
Thanks
Andy