FCL.740.A Revalidation of class and type ratings — aeroplanes
[…]
(b) Revalidation of single-pilot single-engine class ratings.
(1) Single-engine piston aeroplane class ratings and TMG ratings. For revalidation of single pilot single-engine piston aeroplane class ratings or TMG class ratings the applicant shall:
(i) within the 3 months preceding the expiry date of the rating, pass a proficiency
check in the relevant class in accordance with Appendix 9 to this Part with an
examiner; or
(ii) within the 12 months preceding the expiry date of the rating, complete 12 hours
of flight time in the relevant class, including:
— 6 hours as PIC,
— 12 take-offs and 12 landings, and
— refresher training of at least 1 hour of total flight time with a flight instructor (FI)
or a class rating instructor (CRI). Applicants shall be exempted from this refresher
training if they have passed a class or type rating proficiency check, skill test or
assessment of competence in any other class or type of aeroplane.[…]
(4) When applicants hold both a single-engine piston aeroplane-land class rating and a single engine piston aeroplane-sea class rating, they may complete the requirements of (1)(ii) in
either class or a combination thereof, and achieve the fulfilment of these requirements for
both ratings. At least 1 hour of required PIC time and 6 of the required 12 take-offs and
landings shall be completed in each class.
Anyway, since your rating has lapsed, if you like, you can renew your SEP(sea) in Flensburg, aswell.
Here (pages 4-10) is a nice recent report on getting the seplane rating at Aeroclub Como. Not sure if and how in 2023 it still works for UK license holders to get the rating.
@boscomantico thank you for resurrecting the thread, I think the CFI Gabriele may also have UK CRE privileges?