I too freak out about this punkosaur. Always have, always will.
If you’ve got loads of holiday left and don’t mind using it, book a half day.
If not then say you’ve got a doctor’s or a dentist appointment and that you’ll make up the time by coming in early/staying late.
Also in future I’d recommend asking the company you’re interviewing with for an interview time more suited to you. Speaking as a recruiter, I honestly don’t mind being flexible.