CAA lost log book requirements
Please read carefully the information given above. There's too much to paste here but it involves 2 interviews in person with the CAA (and payment of some fees, naturally). At least you're in the same county?
As far as I am aware, log books and other documentary evidence should be kept for your lifetime. I've still got all my log books going back to 1982 and my old brown licence, as well as subsequent ones. I've moved house several times in that interval. I know things can go astray and they might not appear important at the time or (in one case I know of) they might get burned by a jealous ex-wife...
TOO