£55 is certainly greater than £30!
Whether or not £55 represents 'good value' for you, only you can decide. That might depend on a whole bunch of things (including speed/reliability of the service, your options to change to another supplier with comparable speeds etc. etc.)
For £30 p.m. you are (presumably) citing a new customer price versus a long-term, out-of-minimum-term price with VM.
Have you renewed with VM in recent times? Did you try to renew and VM failed to come up with any decent offer?
Outside of your minimum term, VM will just keep 'price-walking' your subscription onwards and upwards until you either renew for a better price or cancel and go elsewhere.
