Handbrake problem

300tdi disco 1. Handbrake seems fine when engine is cold but after a long run, usually a motorway run rather then driving round town, the handbrake gives up completely and doesn't work no matter how hard / high i pull it - bit of a problem doing clutch control at the top of the motorway slip road !
When its parked up overnight, it seems fine again.

Anyone else had this problem or sorted it ?

Thanks

Have you had a look?