Brake pedal sticking?

Twice in the last week I've had a problem with the brakes in my car when reversing out of a parking space. It's a 2003 1.8T Elegance, and on both occasions had been parked all day. I started the car, kept my foot on the brake and put it in reverse as usual. As I was rolling backwards, I wanted to dab the brakes for control, but when I put my foot on the pedal it felt like there was a brick stuck underneath. I pressed down hard with my foot but the pedal wouldn't go down and the car kept rolling. I quickly had to put it in neutral to stop it moving, tried again and the same thing happened. Eventually I managed to reverse out of the space and put it in D and the brakes immediately worked fine. It's puzzling because it's only happened twice even though I've reversed out of parking spaces probably twenty times in the last couple of weeks. Your thoughts, comments and advice would be most welcome.

H

Edited 15 September, 201015 yr by Honeyman