Actually I had completely forgotten, it's already an offence to either fill out incorrectly or fail to fill out the registration form, registration is compulsory, voting isn't
It's up to a £1000 fine at the moment
not sure which authority issues this though
My understanding of the law is that this isn't quite the case. I'm pretty sure Guy confirmed this with the Cabinet Office, that actually you just have to return the form but you do not have to provide any information. Although if you provided false information that would be an offence.
The real issue here as well is what the roll is used for, and what information is contained within it. A couple of years ago the Electoral Commission looked at people providing unique identifiers such as biometrics to help counter impersonation. There is also talk of cross-referencing the electoral roll with other information to ensure people are enrolled. We presume the roll will also then be used for crime prevention and fraud detection.
Before you know it there is in my view a real risk an electoral roll based on individuals could start to develop into something akin to the National Identity Register. Sadly the electoral reformist are so keen to encourage participation that they don't fully appreciate this risk, that could easily have been avoided with an opt-out system as was originally proposed by the Cabinet Office.