Rear light power problem

[phlyer]

Anyone got any ideas.  My 2L cdti has developed an issue that has the fog, reversing and rear right indicator lose power.  The Cambus keeps giving a bulb warning but the bulbs have all been checked and they are all good.  I've also checked the power tracks in the clusters from the cable socket pins to the bulb socket and they are OK too.  

This spreads across 3 of the 4 rear clusters and all the other lights not mentioned are OK.  Same time as this I believe, the dash power socket has also failed.  I've gone round all the fuses and they too are a ll good. 

I'm guessing this means it's a wiring issue,  potentially a plug somewhere that's maybe come loose?   I don't really have a clue other to start checking connectors etc I can find.   

Any ideas on a common denominator?

Tia,