Thanks, the wiring and set up is arranged below:
handset cord -
RED - T1
GREEN - T2
BLUE - T3
WHITE - T10
Dial terminals -
ORANGE - T8 - D5
PINK - T10 - D4
SLATE - T1 - D1
BLUE - T2 - D2
BROWN - T3 - D3
line cord -
red-T8, blue-T6, white-T18, green-T15.
STRAPPING
T4 - T5 - T6
T16 - T17 - T18 - T19
but still no joy Im afraid, its peculiar that all the phones have the same problem... yet cannot seem to break the dial tone - when dialling out, I can hear a tinkling on my extension phone; it sounds like some sort of connection is being made.... Totally baffled!