As long as you provide the statutory minimum holidays you may allow any number of holidays.

Songkick, Eventbrite, Hub Spot and Netflix are among some well known technology based businesses that allow almost unlimited holidays.  Virgin Management, the parent company of Virgin’s world wide operations has offered the top layer of management extended paid leave since 2014.  They believe it has created a happier and more empowered environment which is an incentive for some employees.

If this is something you would like to introduce into your business it would mean a contractual change.  This would require consultation with the employees concerned to get agreement.  This would also be the case if you wanted to revert to statutory levels at some point in the future