CAP 804 Part H says
FCL.740 Validity and renewal of class and type ratings
(a) The period of validity of class and type ratings shall be 1 year, except for singlepilot single-engine class ratings, for which the period of validity shall be 2 years, unless otherwise determined by the operational suitability data, established in
accordance with Part-21.
(b) Renewal. If a class or type rating has expired, the applicant shall:
(1) take refresher training at an ATO, when necessary to reach the level of
proficiency necessary to safely operate the relevant class or type of
aeroplane; and
(2) pass a proficiency check in accordance with Appendix 9 to Part-FCL.