I was brought up in the UK.
I'm mostly left-handed and always use my left hand for the fork and right for the knife. If I'm just using a spoon it will mostly be my left but not always. If it's something served with a fork and spoon then it's fork in left and spoon in right hand.
I'm not sure left-handedness comes into it that much with me. I just use the utensils the way I was taught except possibly for the solitary spoon thing.
Like
Steel Icarus 's former F-I-L, I was taught it was polite to eat peas by combining them with something on the back of the fork. I don't always adhere to that rule when I'm eating on my own.
ETA: If I'm preparing food then I tend to slice things with a knife in my left hand.