Today I tackled the flickering brake light problem and with advice from others on here , managed to fixed it.
I removed the lid and grasped it firmly, then firmly twisted the aluminum cylinder off the stubby base inside the lid and this is what I found......
The cork was saturated with brake fluid and was too heavy to rise up the tube to make contact with the electrical terminals at the top.
I then carefully cut the end of the shaft off , it had been squashed at the very tip and that was what held the cork and tiny washer on.
I found a champagne cork and cut the humps off its sides, then ground it to a perfect round that fitted the cylinder with clearance to allow for possible swelling.
I used the same method of fixing it onto the cork as the factory used, I squashed the tip in a vice to retain the washer and cork thus.....
then pushed the aluminum cylinder back onto the stub , it was a tight fit anyway , and replaced the lid to the brake reservoir . The brake light did not come on .....job done.
I hope that this will be of help to others , if this proves to be the problem..
Peter