I've just took out a broadband package with Bt, their deal ends tomorrow for BT unlimited 52mb fibre broadband and unlimited weekend calls for £28.49 a month. So going through topcashback.co.uk got me £84.24 in cashback. I have also got a £125 prepaid Mastercard as a new customer. There was a setup fee and delivery for router of £59.99. So working this out £28.49 x 12 = £341.88 + £59.99 = £401.87.
Minus the £84.24 cashback and £125 prepaid Mastercard gets you £192.63
Divided into 12 is the equivalent of £16.05 a month!
The reason I put for £14.15 a month is because there is an option to pay your line rental off in full saving you a further 10% off line rental, based off the same amount of cashback I worked it out at £14.15 a month equivalent.
Cancelling my sky account they couldn't even come close to matching price wise.
There are also good deals for BT sport and half price sim only offers when taking out the contract online to further savings.
Hope this helps