Depends what you mean by permit to fly.
1 issued by the LAA or CAA etc for aircraft without a TCDS. Depends where abroad and what restrictions they have.
or
2 issued by EASA via the CAA for aircraft with a TCDS but no valid C of A - eg out of check or damaged. An EASA Permit to Fly is valid in all EU Member States, however, national operational requirements remain applicable.