Heh. Looks like I made the wrong move then

I smooth called. I was worried about UTG slow playing a monster. Thought process went:
1) If either SB or BB raises, I'll see what UTG does. If he moves in, I get out. If he folds, I probably call the raise and hope to win the race.
2) If SB or BB calls, I'll see the flop and evaluate from late position but almost certainly muck unless I hit.
But I bow to popular and sensible opinion which derides my call!
As it turned out, SB and BB flat called and checked respectively. I was surprised SB didn't move in but I think she was also worried by the UTG limp because it seemed so unusual for this guy.
The pot was now 32k.
The flop came

. I had one spade, a weak overpair to the board, and an inside straight draw, and 72k chips.
SB and BB checked. UTG puts 24k into the pot, leaving him with 30k. What do you put UTG on, what's your move?
Hope you haven't got your coat yet Tikay!