The piece looks way too short to be a flaperon from a B777. From the second photo in Telegraph article, it's at most 2.5 m long. B777's inboard flap is at least 5 m long. Either it got snapped in half (doubtful, since both edges look straight), or it's not from a 777.
The flaperon on a 777 is an inboard (IE high speed) aileron. Not a high lift device such as a flap. Its called a flaperon because when flaps are selected down it droops with the flaps but can still modulate up and down to control roll.
That looks like a flaperon to me, and unless there are more missing 777s that we don't know about. Its a good bet its from MH370.