Kitty, you are right I've never heard of it either!
But here (Hants) our kids get the Friday and Monday off, go back to school for 2 weeks and then have their 2 weeks off!
I even phoned the LEA to check and they agreed it was unique!
Most of our friends in other parts of the country are the same.
Make hay while the sun shines if I was you as that is probably why you can get it so cheap!
As I said may take the kids out of school for those 4 days if I can get a cheapy in!