Maybe I'm confused by what you've said John....
But You tick the box on the electoral form to opt out of the EDITED version. People choose to opt out to avoid marketing, junk mail, cold calling etc...and if they want to make it dificult to be found!!! This is the version viewable. Also the same data as the UK Info Disks.
However, nobody can opt out of the FULL electoral roll

.... well you can, but you may get a big fine!

Unless maybe if you'r in prison
The Full electoral roll is held at Electoral Libraries all over the UK. This is used by the 3 main credit referencing agencies and such like. But the general public CAN see the FULL electoral roll. However, you can only use it to confirm an address. You can also phone the libraries and dependant on whoever answers, they may help you!
There are other means of searching, but often NOT by the public. Most search facility's available online are the Edited electoral roll....which the majority of people now opt out of.