Auto box problems

Fellas, I noticed yesterday that the auto box on my TD5 seems to be playing up.

From memory, I recall that if left on a slight slope, with engine off, the transmission would 'lock up' in 1,2,3,D, R & P, but the car would roll down the slope if left in N. (with no handbrake applied). That is how it should be isn't it? Or am I going utterly senile?

Yesterday, the vehicle exibited a tendency to roll on in all gears except P.

The car has done 80K miles, tows a fair bit, but hasn't been abused.
When driving everthing seems normal, no warning lights on the dash, no odd noises.

Have I got a problem, am I doing something wrong?

It's only locked in P.

I called in at the local garage when I was out and about.. they said it was working right, so apologies all, I must have had some sort of brain storm... idiocy on my first post, I will try and up my game in the future,

park is a pawl thats pushed into castellated wheel in rear of box and can be broken easily especially if you select it while rolling,use hand brake as well