The flying time from London to Florida should be under 9 hours on a direct flight. The time could vary greatly depending on whether or not you have layovers and what part of Florida you're flying into.
The actual flying time between London and Paris depends on the specific route and airline that is used. The average flying time between these two locations ranges from 55 minutes and 1 hour and 20 minutes.
This depends on wind speed a little but generally it is just over 10 hours from London to Houston (10 hours and 10 minutes) and between 9 & 10 hours from Houston to London. It is typically faster going from Houston to London because of the direction of prevailing winds.