My manager will chase me up if my vacation time is going unused (e.g. I get 1/2 way through the year with less than 1/4 of my vacation used) and ask me what my plans are for using it.

Getting to the end of the year without using it all up is considered poor planning by the employee and poor management by the manager.

I get 27 days (on top of the UK public holidays). So I try and have a week per quarter, plus an extra week around Christmas/New Year.

This is in the UK, but I had the same thing with an enlightened manager when I was US based.

Are you able to put them between weekends?