Aircraft heading NW, G/S 250kts (50nm/12mins=250kts), ie faster than TAS of 225, therefore tailwind! So wind is from the south. You chaps should know when there are 3 similar answers, the real answer is one of them, not the one on its own!
Londonmet- either use a circular slide rule or draw out a large accurate triangle- you have two sides (250 and 225) and the internal angle- the third side is the wind speed and direction- convert to degrees True.