Here's the relevent extract from LASORS...
F1.5
RENEWAL OF SINGLE-ENGINE PISTON – SEP (LAND), TMG CLASS RATINGS
Where licence holders have been unable to renew a SEP (Land) or TMG Class Rating for a period not exceeding 5 years from the date of expiry, they will be required to complete the following requirements:
i. The CAA will require no mandatory additional training. Applicants should complete training at their own discretion sufficient to pass the Skill Test.
ii. Complete the Skill Test in accordance with Appendices 1 & 3 to JAR-FCL 1.240 with a JAR Authorised Examiner. For renewal of an instrument
rating if held, please refer to Section E1.5.
iii. Pass an oral theoretical knowledge examination conducted by the Examiner as part of the skill test.
iv. A UK Authorised Examiner can sign the Certificate of Revalidation page (FCL150CJAR) within a UK national pilot’s licence. An Examiner qualified in
accordance with JAR-FCL (in any fully compliant JAA Member State) can sign a Certificate of Revalidation page within a JAR-FCL licence. The
LST/LPC form, completed as a renewal, should be sent to CAA PLD.
v. The CAA will charge no fee provided that the Examiner signs the Certificate of Revalidation.
Where licence holders have been unable to renew a SEP (Land) or TMG Class Rating for a period exceeding 5 years from the date of expiry*, they will be required to complete the following requirements:
i. The CAA will require no mandatory additional training. Applicants should complete training at their own discretion sufficient to pass the Skill Test.
ii. Complete the Skill Test in accordance with Appendices 1 & 3 to JAR-FCL 1.240 with a JAR Authorised Examiner.
iii. Pass an oral theoretical knowledge examination conducted by the Examiner as part of the Skill Test.
iv. The LST/LPC form, completed as a renewal, should be sent to CAA PLD for endorsement, together with the appropriate fee as per the Scheme of Charges.
v. The Examiner should make no licence entry.
For renewal of an Instrument rating, if held, please refer to Section E1.5.
*Where an applicant can show that they are currently flying under the privileges of an ICAO licence, and are flying the same aircraft type/class within their UK or JAR-FCL licence, the renewal requirements will be based on the expiry date of the rating currently being exercised.
Best of luck
TCF