I fill in my electoral role each year and always tick the opt out box. It would appear that my council say they did not recieve it this year and as a result have sold last years data and I now appear on the edited register and am trying to find out if they can legally sell my data without my consent like this?
If I read your question correctly it's the case that your Council has added you to the current version of the electoral roll without marking your record as 'opted out' because they didn't receive your registration form. If so, I suspect they have breached the Data Protection Act. If they didn't have your registration form they shouldn't have added your details to the roll; let alone assume that you'd want to be included on the edited version of the list (you were opted out in previous years, so on what basis would they have not opted you out?).
If it's the case that your Council retrospectively unmarked your record as opted out the situation would be even worse, but I suspect that's not what happened.
It might be worth clarifying with the Council what exactly has happened. You then may want to give the Information Commissioner's Office a ring on 0303 123 1113. The Information Commissioner's Office is the body enforcing the Data Protection Act and its helpline is usually very helpful. You may also want to contact the Electoral Commission via its About my vote website, although they tend to be rather less helpful.
Finally, it's not uncommon that electoral registration offices make errors. Unfortunately, 'opted in' is still the default option…
Update
From June 2014 you no longer need to opt out annually. If you're currently opted out of being on the edited register – which has been renamed open register – you'll be opted out on future editions of the roll as well.