FAQ: Can I take part in my employer’s plan?
Share Incentive Plans are all-employee plans, so they cannot be restricted to particular groups or individuals. However, companies can exclude employees who have not worked for the company for a minimum period of time. Individual companies can set their own minimum limit, but it cannot be longer than 18 months.
Part-time employees have the same rights to join as full-time employees.
You can take part right up to retirement. Income tax and National Insurance advantages will remain in place if you take your shares out of the plan early because you retire at or after the age specified in the plan rules.
Source: Inland Revenue