Spotted this & thought it was worth putting on here. - You can get a BT line installed for free untill 30th September. This is a massive saving as usually it would set you back £122.50.
This applies to new lines, reconnections or even having second lines fitted and isn't dependant on already having a master socket.
The only catch is, you have to sign to an 18 month contract, rather than the usual 12, and you'll need to make at least ten calls per month but these can be inclusive calls if you get a BT package & line rental from only £11.25pr month.
This isn't available online : to get it you need to ring 0800 800 150, lines are open Monday to Friday 8am to 9pm, Saturday 8am to 8pm, Sunday 9am to 6pm. When you call, ask for the 'New line free connection offer'.