Hi All - to help others who have this problem or are thinking of changing their amber/red to OEM clear/red - beware your wiring looms might have different pin configurations..... :-( It may not be the straight plug & play that the dealers say it is - mine wasn`t!
I took it to a BM Specialist in Hove who was brilliant, understood the problem and some soldering/wires and bridging later its all working :-)
Basically, my rear wiring harnesses were:- 1,2,5,6,7,8 wired up but 3,4 not populated. On the new cluster we had to put a new pin/wire into No.4 and bridge/feed from No. 8, on mine was purple & grey.
The right cluster (which seems to feed the left and centre) was only lighting 1 of the 2 bulbs used for the side lights and not passing power round to centre or left cluster either. My wiring was 1,2,3,4,5,6,7 with 8 not being used, however on the new cluster the config was different with 3 being empty. We put a new pin/feed into 3, bridged no`s 2 & 3, and also 4 & 8.
Whilist looking online there seem to be 2 different wiring diagrams for the same car for same year - '2 pins' and '4 pins' diagrams - I reckon my car was 2 pins but the clusters were for the 4 pin setup.
Superb - all working and never to be touched again!!