Save over £600: Vodafone Full Fibre 910, 24-month minimum term (450 Mbps average download speed): £28 a month for 24 months (total = £672), vs BT's Full Fibre 900 and phone package, 24 months (72 Mbps average download speed): £52.99 a month for 24 months, plus £31.99 upfront (total = £1303.75).