The fairly standard 12 months half price ADSL2+ with a £50 M&S e-voucher now has an end date of the 7th July 2015.
In addition if you scroll down the page linked above, there is an offer giving 12 months free unlimited ADSL2+ with free Sky Box Sets if you subscribe to the Family Bundle at £30 per month with the added bonus of a 32" Samsung TV or Sonos Play:1 Speaker.
Existing Sky TV customers appear to have an other to upgrade from free if they call 0800 151 2766
Voice line rental at £16.40 per month applies to any Sky bundle that includes Broadband
Sonos Play:1 speakers retail for around £169