Annual Holiday

I’m fortunate enough to still be working from home but my employer is now insisting that I take 8.5 days holiday, which is a third of my annual allowance, before the end of June. I’d really rather not take my holiday now as obviously I can’t make the most of the time off. I thought there was a way that I would be able to roll over the holiday onto next years, or is this not the case? Thanks in advance.