No or yes
sounds as though you have the 300 version light with no indicator ( no amber plastic) in your unit
NOT like this
LAND ROVER DISCOVERY 1 REAR LIGHT CLUSTER OFF SIDE on eBay (end time 07-Mar-11 20:43:04 GMT)
But like this
Discovery 1 Rear Light / Brake / Reverse Assembly RH on eBay (end time 13-Mar-11 21:17:01 GMT)
From Rave for left cluster
C403
B121
Left Rear Lamp Assembly
[1] Rear Fog Lamp
[3] Reverse Lamp
[4] Stop Lamp
standard offering for a while on 300's, mine a Feb 98 one was same
you can change the units if you want indicator and rear lights higher up,
----------------------------------------------------------
reversing lights
green / brown wire off the rear light cluster
and check you have some power there when you have it in reverse with ignition on, AFTER you check the lamps, then go to the left side of gear box, and check out the switch (one green / brown wire connector) put a power source on this and reversing lights should come on, if no light a wiring fault, check for power out from the connector, if not switch faulty