After messing around with the dash bulbs in my Felicia I've found that the brake warning light (!) is now permanently on - the bulb must have been blown or intentionally swapped out for a non working one. 

I never noticed before since most cars I've had only had one light for the parking brake and brake warning, whereas the Felicia has both a (!) and a (P).

 

The brake fluid is not low and is not leaking - it could do with a change though. 

 

The sensor appears to operate in that the resistance at the pins changes if I remove the cap from the reservoir simulating an empty fluid reservoir.

Is the wiring at fault?  Do the wires from the sensor go straight to the back of the instrument panel?

Do this test:

- disconnect low fluid level sensor connector

- key on and watch warning light

- key off

- short sensor connector pins

- key on and watch warning light

 

If warning light stays on in both cases, you fried something on dashboard PCB while 'messing around with the dash bulbs'.

Thanks, I'll check it out.  If the light goes out, is the sensor faulty?

Thanks, I'll check it out.  If the light goes out, is the sensor faulty?

Yes. Sometimes it gets stuck.

I would change the brake fluid in the process too.