Pay a lot of money to get a new flight ticket anyway. Better inform the airline you won't be using the one on the 24th to avoid trouble down the line.
Jump through bureaucratic hoops and spend a lot of money to try and change your visa in line with your plane ticket.
Take another trip in addition to your UK trip. Venezuelans have visa free access to the Schengen zone- on the 17th or 18th leave to the UK to go spend a week visiting France, Italy or wherever you fancy/get the best deal, and then fly back to the UK on the 24th to transfer to your flight back to Venezuela.