SolvedETASSUM42180 | Schedule 4 Company Share Option Plan (CSOP): Eligibility of individuals to participate: The employment requirement: Exercise of options
From HM Revenue & Customs · Employee Tax Advantaged Share Scheme User Manual
Paragraph 8 only requires option-holders to be current employees and directors when the option is granted. There is no requirement for the option-holder to be employed when the option is exercised.