Has anyone got any luck with Austro Control or Malta CAA. I am currently in a similar situation trying to transfer my UK CPL to EASA ATPL. I was able to receive an email from EASA itself prooving that ATPL exams are still valid for 7 years if it was obtained under UK CAA before 2021 or 7 years since last IR rating validity. Clarification of the regulations is only a Google click away, either Part FCL or FCL.025 (c )(2) which confirms:
(c) Validity period
(1) The successful completion of the theoretical knowledge examinations will be valid:
(i) for the issue of a light aircraft pilot licence, a private pilot licence, a sailplane pilot
licence or a balloon pilot licence, for a period of 24 months;
(ii) for the issue of a commercial pilot licence, instrument rating (IR) or en route
instrument rating (EIR), for a period of 36 months;
(iii) the periods in (i) and (ii) shall be counted from the day when the pilot
successfully completes the theoretical knowledge examination, in accordance with
(b)(2).
(2) The completion of the airline transport pilot licence (ATPL) theoretical knowledge
examinations will remain valid for the issue of an ATPL for a period of 7 years from the last
validity date of:
(i) an IR entered in the licence; or
(ii) in the case of helicopters, a helicopter’s type rating entered in that licence.
The email states you cannot simply swap the licences but then says that individual states can accept your training / qualifications if you apply for a licence.
Therefore your TK exams are valid for 7 years from the last IR and you should not need to take them again.
You obviously would need to take an EASA Class 1 medical for the state you wish to apply for an EASA ATPL licence