You mean like this?
The extension sockets should be connected to where the red arrow is pointing.
A short note to thank everyone who offered solutions to my LINE NOISE problem.
Very much appreciated.
I followed up all the suggestions but was still left with a very noisy line.
As a last shot I went out and bought a NEW HANDSET from Argos for £6.99 as a last resort!
To my amazement THIS WORKED and the line was suddenly ABSOUTELY SILENT - NO NOISE AT ALL!
I tested the line using the BT LINE tester (Dial 17070 and then press KEY NUMBER 2 for "Quiet line test"
and there was NO DETECTABLE NOISE.
The moral of the story appears to be "Don't ignore the obvious"