Talktalk with cashback, EE if you have an EE phone or work discount. Plus the various tiers before you came up with an arbitrary 100mb limit. ie VF are doing 500meg for £32 a month (£29 if a mobile customer).
I also suspect this is just the start of a bit of a war, given VF are passing on the Openreach wholesale price drops and with everyone bumping prices up there are lots of customers to be grabbed.