My FF SC 2008 runs very lumpy and misfires when when cold for about 5 mins then runs fine after that, iid tool tells me that bank 1 is running rich and misfires on all 8 cylinders under 1000RPM, when warm switches to LPG and runs fine.

Any help would be welcome

Have you run the car on petrol from time to time, I mean a good petrol run (say 60 to 100 miles). If you haven't done that, the petrol system may have clogged up a bit, causing the cold run issues.

Another possibility is the fuel filter having clogged up. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Runs everyday on petrol for a short time will change the petrol filter and see how it goes, but i would have thought if its not getting enough fuel it would come up running lean? not rich?