Check the solenoid connections.
If your hearing a clunk off the solenoid, then it sounds like the coil side of the solenoid is ok. Get a test lamp / meter over the bigger terminals and an earth. You should have 12V at one of the terminals with the isolator on. If not, the fault is upstream of the solenoid. You can test this by carefully putting a jump leads on the motor, and seeing if it runs.
If you have 12V on one of the larger solenoid terminals, put your meter / test lamp on the other side, try and send the body up, if the light comes on or the meter shows 12V, the solenoid is ok, and the motor is faulty. If this is the case, give the motor case a good couple of hits, and see if it works then. (worn brushes).
If there's no power on the other terminal, and the solenoid is clicking, the solenoid is goosed, there about 20 quid depending on the size of the motor.