The "my offers" section is offering 20Mb to 100Mb for £5/month. Perhaps if it's done in 2 stages the offer becomes 90p/month.
My modem was replaced recently by a superhub, so there is less additional cost involved for VM.
Looking at the "build a bundle" section, 100Mb with my current loyalty(10 years) discount should mean £10/month less than I am paying.