TalkTalk are offering 3 months free on their Essentials and Plus packages with free standard setup and a free wireless router.
TalkTalk Essentials
TalkTalk Plus
For those in fibre-enabled areas, you can get TalkTalk's Fibre Optic Boost for an extra £10 a month with both Essentials and Plus packages.
TalkTalk Essentials with Fibre Optic Boost
TalkTalk Plus with Fibre Optic Boost
Line rental required at £13.80 a month, or save £51.60 by paying for a year up front.