Plusnet are offering 12 months half price on Value Broadband packages when you sign up for one of their phone deals. Prices are from £3.24 a month:
Plusnet Value with Home Phone Evenings & Weekends
Plusnet Value with Home Phone Anytime
Line rental of £11.99 is required for both packages. Evening and Weekends call plan included as standard, Anytime call plan costs £3.50 per month.