If you are currently flying on a CPL or ATPL then you would need
to apply for a PPL and surrender your CPL/ATPL (only one Licence,
per aircraft category, allowed under EASA).
Part-Med.A.030
(f) Applicants for and holders of a commercial pilot licence (CPL), a multi-crew pilot licence (MPL),
or an airline transport pilot licence (ATPL) shall hold a Class1 medical certificate
FCL.040 Exercise of the privileges of licences
The exercise of the privileges granted by a licence shall be dependent upon the validity of the
ratings contained therein, if applicable, and of the medical certificate
PPL privileges are "granted" by virtue of holding a CPL or ATPL, but
CPLs and ATPLs are not valid unless a Class 1 Medical is held.
CAP804 Section 4 Part N p1
2 Privileges
In order to exercise the privileges of any licence, a pilot must hold a valid medical
certificate for the licence held.