You say you have three wires on the light fitting and they're, "green / yellow and blue".
My guess is that you have only identified two of the three wires and have failed to tell the colour of the third wire.
You will be safer having a qualified person making this repair.
Lord Finchley tried to mend the Electric Light
Himself. It struck him dead: And serve him right!
It is the business of the wealthy man
To give employment to the artisan.
Peccavi
October 2008