As mentioned earlier, if he moves to United then you'll definitely be rewarded.
However, if he moves anywhere else (Real Madrid etc) then I think you'll see a loss which I don't think he will recover from. He's already got the Premier League premium factored into his price.
In situations like this, I normally just go onto Sky Bet and put £10 on him to move to United to get it out of my system so I'm a winner either way haha. Good luck with whatever you go for though!!