Bosch WFL2000uk/01 - possible to repair?

At that age, there is a chance that the carbon brushes could have completely worn out. However, it's a bad idea to guess at parts. You need to take off the motor, and inspect the carbon brushes to see if they are actually worn. This article gives a good idea on what to look for - Washing machine carbon brushes

On a modern washing machine, if the motor was not running, that would be detected, and the wash cycle would be aborted followed by the washing machine displaying some error code. But on a washer machine as old as that, it's unlikely to have any error codes system.

So on an old washing machine with worn out carbon brushes it would fill up with water, and just sit there for 20 minutes or so doing nothing other than heating up the water. When the water has reached the correct temperature, it should pump out the wash water and go through a cycle of filling with cold water, sitting there for 4 minutes or so, and then pumping out the water. In other words, it would go through all of the wash and rinse cycle, but the drum would just never turn.

Although worn carbon brushes is definitely a possibility, if the motor is failing to run, it could be caused by at least half a dozen other things too - Drum not turning during the wash cycle

Having said all that, it's perfectly possible that the fault has nothing to do with the motor at all, and the motor isn't running simply because the washing machine is not running the wash cycle properly due to a totally different fault. There's always the possibility that the door lock is faulty, but on an old washing machine, when the door lock is faulty I would expect nothing to work at all other than the control panel. The door lock is there to prevent the washing machine operating unless the door is securely and safely closed. It's always possible that for some reason your washing machine is designed to allow the washing machine to fill and drain with the door open, but just wouldn't let the motor run. I can't think why they would do that though.

Loud clicking noises could be something to do with a faulty relay, or faulty components inside the main PCB, or even connection or power supply problems. Basically at 22 years old, unless it is something very straightforward, I genuinely don't think it's worth spending time and money on. Even though modern washing machines are rubbish in comparison, at the end of the day it doesn't matter how well something is made, they only last so long.