Blocked Bath cleared from £29.95 in Seven Kings
The wrong way to unblock a bath plug
Traditionally people would clear it with a bent wire (and old clothes hanger was always the tool of choice when i was a lad).if you have a plastic wastepipe, then scratching it with a coat hanger as you try to clear the blockage can lead to burrs where hairs can collect in future, leading to a repeat of the problem.
You may be tempted to unscrew the plughole cover for easier access, but the screw holds the wastepipe in place, so if you do this then the bath full of dirty water is going to run all over the floorboards beneath the bath, which could cost a fortune to fix. Leave the screw in the plughole well alone.