Hi,
The guidance at below advises that you will not pay capital gains tax if you transfer the shares to and ISA withing 90 days of the scheme ending.
Tax and Employee Share Schemes
If you do not transfer your shares to a pension immediately when the scheme ends, you can still transfer them up to 90 days later. You may have to pay Capital Gains Tax if they go up in value between when you buy them and when you transfer them.
Thank you.