Table is playing 5 handed, Villian has just sat down recently. He is unknown to me but is young. The Black Nelt tourney is on so there are presumably plenty of unknowns (to me) in town for it both good and bad. Not seen too much to asses his post flop play but he has open limped a few times and open minraised.
He has about £400 (bought in for £500) and I cover
Dem aces UTG (5 handed) I open to £15 my standard size at this table American mike folds

Villain flats the button Both blinds fold
Flop =

Hero bets 20 V calls
Turn =
H bet 45 V calls
River =

Hero??? Not just what my action should be but what should my response to his reaction be?