Brava Left indicator slow?

The car is going in for its MOT on monday and the left indicator is playing up, when I brake when the indicator is on it goes from normal speed to really slow/to a near stop and speeds up to normal again once the brake is off.

I dont know a great deal about the inside of my Brava I do have a haynes manual and the Brava owners book that came with the car, but there is nothing in there about anything going wrong like this.

I'm sure "indicators" not working right are an MOT failure?

If so any ideas what the problem maybe as hoping I dont end up with a huge repair bill

Thanks

bad earth, from dirty contact

first thing to do is disconnect the light's wiring connector, check it is clean, give it a spray of WD40, and then reconnect it and hope for the ebst. failing that you need to check the earth point in the boot and clean it up (remove, clean with sandpaper, grease, refit).