The full electoral is only available to District, County and Unitary Councillors, MPs, MEPs, registered political party's and  the Returning officer.

Not really. Though the data is updated quarterly, the information in the electoral rolls need not be complete because-
a) Only the abbreviated version is made available for online searches; The detailed list can be used only by those having the legal right to do so, such as electoral supervisors.
b) the list might not contain  the  names of voters who choose to "opt-out  from this list .

The Electoral Register includes the names and addresses of most UK citizens over the age of eighteen and that makes it one of the most  popular sources to find people and also for job related searches of employees and employers.

There are many online directories that help you to search people from electrol rolls.

Some of the popular sites include:-
http://www.192.com/people/
http://www.1stlocate.co.uk/
http://www.theukelectoralroll.co.uk/
http://www.ukroll.com/
http://www.ukphonebook.com/?cd=register&from=er