Can I extend my France Visa from UK during my France trip?

No, generally you can not extend your France Schengen visa from UK. It can only be extended in unforeseen situations like:

• Health emergencies where you can not take your flight or are unable to reach the airport.
• In any major natural crisis, like an earthquake, a cyclone, or a flood.
• If there is a human-made situation, like war or any unsettled political issue.