NO you do not use your PPL. You use the rights of the license that you hold and the class rating on it.
I was told by the CAA that we revalidate the rating, so in this discussion the SEP rating. The next licence in the chain replaces the previous. If you give up flying commercially for example retire. You will lapse to a Class 2 medical and an SEP rating but you will still hold the ATPL license even if all the other ratings on it lapse.