Had the car battery replaced a couple of weeks ago, and although it is probably unconnected, in the last few days have had a problem with hard brake pedal when starting in the morning and leaving work. The pedal is hard for just 3-5 seconds after turning the key, then the brakes operate as normal. There is no mid-journey brake problem. Took it back to garage, they've had the wheels off and gone under the bonnet and tested for leaks and vacuum but couldn't find a fault. So they replaced the one-way valve which they thought might be not working as efficiently as it could. But this didn't resolve the problem. They are now suggesting the only other thing might be the servo. Anybody any other ideas? Thanks.