Entertainment book seems to now be moving to rolling subscriptions that can be activated at any time, rather than financial year based subscriptions. You do need to read the fine print to make sure that this is right for you if you are renewing an existing subscription, but it could be good value for people who are not renewing.
Up to 4 months extra Membership applies to activated Single City and Multi City purchased between 8th February and 29th February 2020. From time of purchase, an Activation Code must be activated within two months. If activated within two months, the Membership will expire 16 months from the Activation Date. If not activated within two months, the Membership will expire 18 months from the Purchase Date.
My entertainment book is due to expire on 2/6/20. If I purchase it on 29/02/20, I can get a membership through to 29/08/21, so about 2 months extra.