How could I improve?

Just won this game with campion, how could I have played better? Any obvious mistakes?

6...d6 actually increased the mobility of the light-squared bishop (although it did decrease the mobility of the dark-squared bishop whose mobility is already limited).

 White's move 8.Bg5 hangs his Bishop.  I would've taken it.  As is, the move you played blocks your Knight and weakens the pawn barrier that will be in front of your King if you decide to castle Kingside. (I'm annotating this as I click through your moves, and I haven't seen the conclusion of your game yet.)

 After 10. Bg3 his bishop is really hemmed in by your pawns.  10...g4 actually releases his Bishop.

You got lucky and White played 11. Qf4, hemming in his Bishop which you'd just released.  If I had been playing White, I would've backed off my Queen to d2 or c1 (probably c1 to avoid taking the d2 square away from the Knight, which cannot be developed to c3 because of your pawn.

As for 11...Be6, I want to know why you wanted to trade your Bishop for his.  Most of your pawns are on dark squares, which means that your light-squared bishop is worth more than it's dark-squared counterpart because it isn't hemmed in by your own pawns.  In fact, the Bishop that is on the same color as its pawns is often called the "bad Bishop" while the Bishop that is on the opposite color is called the "good Bishop".  White's light-squared bishop is bad while yours is good, so the Bishop trade actually favors White.

16...Bf8 illustrates this point further.  Now your dark-squared Bishop is quite hemmed in, although it does add pressure to your d6 pawn which was attacked twice but only defended once.  All in all, at this point I'm itching to see how you manage to win after what appears to be a fairly well-executed attack with the goal of checkmate.

Watch out for "holes" in your pawn structure-these are places where your pawns cannot attack, and they are great places to post pieces such as Knights.  Watch how White manipulates his Knight through the moves Nc4 and Nb6+ and you will see what I mean.  Also, do you notice how at this point in the game, your Knight hasn't moved yet?  This is a problem-lack of development can cost you a game.

White's move 19. Nxe7 is weak because it trades his Knight (which has been finding all the great holes that I mentioned before up till now) for your bad Bishop.  Normally, if you have a bad Bishop, you want to trade it for a Knight.  Your reply, however, should've been Nxe7 instead of Qxe7, since this move would've helped you get your Knight into the battle and would leave your Queen on the light squares where it has greater mobility (remember "good" and "bad" Bishops?).  Nxc7 would've also defended your Rook from the Queen, since the rooks would then be connected.

And now we come to 20...Nh6.  You finally got it off the back rank.  But as Chessplayers sometimes say, "A Knight on the rim is dim."  Your Knight now doesn't have much of anywhere to go except for f7 (a bright spot in the position for you).  Nevertheless, I would've probably played this move because it (1) connects the Rooks and (2) gets you on the road to getting your Knight to a place where it can help defend (Nf7-e5 and possibly from there to c6).

21...Qe6 isn't such a bad move in and of itself, but if you were just going to put the Queen back where it was why not simply play Nxe6 in the first place?

23...Ka7 appears to me to waste time when your Knight needs to get into the battle pronto!

26...Ng4 gets your Knight into one of the holes in his pawn structure, same as he did with his knight earlier.  Only problem is, how does taking control of that side of the board help you?  Perhaps I speak too soon; my rating isn't too much higher than campion's.

I don't see the point in 27. Bf2?? as it hangs his Bishop.  An inportant part of playing good chess, however, is taking advantage of your opponent's mistakes, which I see you did here.

29. Qc6 appears to try to continue the attack on your King, but a Queen does a lousy job of attacking unless backed up by some other piece (except in the case of a back-rank checkmate).

31. Rxe5 allows 31...Qxe5 (a Rook is generally worth more than a Knight and besides, he already took your knight and this is your only chance of a recapture).

32...Rhd8 doubles your rooks, but now they are hemmed in by your Pawns.  Try to double your Rooks on open files (files with no pawns on them) and half-open files (files with none of your pawns on them).  He should've doubled his rooks on his last turn as well, since you didn't take one.

33...Qa2 is a good move since it threatens a back-rank checkmate next move.  His reply is the only move I can find that avoids this checkmate (although you probably saw all this while you were playing).

You played the rest of the game quite well.

Wow PhilipN, fantastic annotation you've made for me, thanks so much! I read through it all twice and I now see where I made obvious mistakes. One thing though, you suggested that very early on he hung his bishop and I should have captured it? Well actually that's wrong because if you look closer - had I captured his bishop my queen that was defending the pawn on f7 would have moved, and his queen would have captured it - thus checkmating me.

 Also - johnny-on-the-spot your suggestion is a great one - except that he would have played  Qxd6 forcing a queen trade.

Thanks so much everyone!