Any online search (or a search using a commercially available CD) will only search the edited electoral roll. Most people now put a tick in the box, on the electoral registration form, which removes their details from the edited roll (which is available to mailing organizations, etc).
The full electoral roll, in electronic format, is only available to authorised bodies, such as the police and credit reference agencies. To view the full roll, you'll have to consult the paper version (which is listed in street order, not in alphabetical order of surnames) which can only be consulted locally (in public libraries or at council offices).
Chris