RESULT:
After some deliberation I decided to muck the A-J. I find the frequency of bluffing is reduced when a man is all-in and his line looked like an over-pair or a set imo. UTG villain tabled

for middle pair....and bb villain showed J-x to scoop a nice 21k pot and keep him in the tournament.
Now UTG villain took a lot of stick from the other players at the table (not from me) for this play, because of course I send bb packing with the A-J if I don't get pushed out. Attempting to justify his strat to the critics UTG said he put me on a FD 100% and was protecting his hand from being outdrawn. Comments on this? One thing I did take from this hand was flat-calling his flop bet was a good idea...and if bb villain had gone away, UTG with this mentality, certainly double barrels a non-heart turn. I was happy that most of you agreed fold though.
I did allude to the fact that in a 50 quid comp that he wouls be protecting QJ, KJ possibily even J10 etc etc cos your hand is under repped. This is why at this level of buy I like the raise pre.
As played I think you still have to fold and I don't mind your line. For me tho, I like raising here on the button with AJ. In fact I am probably raising with most hands from the button if I'm playing my button