Pre EASA for light aircraft we used to do them 3 yearly at the Star Annual (CofA renewal). ‘‘Twas the climb performance that was usually the problem, with old/incorrect weight schedules and knackered propellers the favourites. Some aircraft, particularly those with pre 1976 non GAMA style POHs/handbooks/manuals, have CAA flight manual supplements with amended climb performance because of the difficulty of making the aeroplanes perform to book. Eg :
https://cwsprduksumbraco.blob.core.w...UP_2_ISS_1.pdf
Now it pretty much only required for imports and occasionally to validate (non) performance changes with some modifications, we sometimes do them electively after major repairs/rebuilds.
CAA check flight handbook :
https://publicapps.caa.co.uk/docs/33...38%20JAN17.pdf
Check flight schedule for simple singles :
https://www.caa.co.uk/media/43ajy4y5...stribution.pdf
CAA check flight page :
https://www.caa.co.uk/Commercial-ind...Check-flights/