Bose X - The purpose of the affidavit would be so I can take my new log book back to flying schools to be stamped again correct?
No.
The prupose of an affidavit is that it is a legal document that evidences that you have sworn, and your oath has been witnessed, that what you have said or written is true (to the best of your knowledge and belief). I expect you will need the swear the oath before a Public Notary and pay some where between £30 and £70 for the privilige unless you have standing arrangements with a solicitor in which case they might not charge.
These days it is far better to keep your log on a computer and make sure you do regular backups (as you should any one) but hindsight is a wonderful thing.