The buzzing is due to no isolator at all most of the time,
The correct way to split a ntl cable signal is with a high qulity splitter E.G a vocom qamtex splitter like this one
http://cgi.ebay.co.uk/3-way-splitter...ayphotohosting then spit it inside the gray ntl dop box outside your house then take some high qulity cable E.G rg6 or i use rg11 or wf125 myself then take a cable to each room then in each room you need a isloator like this qamtex one
http://cgi.ebay.co.uk/ntl-cable-sky-...QQcmdZViewItem in each room you put a cable in to,