Evade charges for BT line installation - save £122-50

[#1]

See http://www.money.co.uk/article/1004122-free-bt-phone-line-installation-offer-extended.htm
BT have extended their free BT line installation offer until the end of September, allowing you to get your home set up with a BT line for absolutely nothing (usual cost is £122.50).
The offer is open to all new, existing, and returning customers, allows you to have a free new line, a reconnection, or a second line fitted.
To get your free BT line installed, simply call 0800 800 150 and ask for the 'New line free connection offer'. The offer is not available online.
There are certain conditions, but apart from an 18 month contract with BT home phone, they don't seem too onerous.
You could always (optionally) switch to PN after the 18 months are up.

[#2]

I wonder if that is a good way to get a new line - with new master socket in a property that does not have one?.
Set up this new line and then cancel the contract on the original line ?

[#3]

It seems that you'd be landed with a hefty charge and a disconnection fee if you did that.
I think you would have to sit out the 18 months first.
There's nothing to stop you using the line for somebodies broadband in the meantime...