I too am without class 1/2 and hold ATPL. But don't want to downgrade ATPL to LAPL.
I have obtained NPPL doctors declaration, very simple visit to GP with form from NPPL WEBSITE see LAA.
application details on that site for NPPL and SSEA "simple single engine aircraft rating".
photocopy all relevant licences logbooks etc and get stamped by a CFI/ FI etc at flying club.
Send cash and wait two weeks.
Simples....