Peugeot 307 starts and runs ok but when starting again after first trip to shop it will missfire until i rev a bit tnen ok

car would missfire in warm weather for first journey of day, and then each start even after being left ten mins.
Now in cold days it starts fine first time but missfires on later starts, had O2 sensor fitted but no good
Peugeot service on phone said a hot or cold sensor may be it. I need expert with Peugeot Planet or Diagbox package Ive been told
I appreciate any help, Thanks, Peter