Just some quick thoughts has i go through game. 4...Bc5 or 4... g6 are more active, but 4...Be7 is ok too. Instead of 8...h6 , 8...Na5 killing the ruy-lopez bishop could be better. White's opening play has been very unthreatening. 11.Bxc6 a lot of people on chess.com don't seem to like their bishops, very strange.11...Bxc6 avoiding damage to pawn-structure for a risk free plus. 13...f5 looks like a natural move, black should be looking to open up position for his two bishops. Sequence with 13...Bg5 spent a few tempo's exchanging off one of your two bishops, which should have been one of white's aims. Position after 15 QxB white has a plus. 20...Rbe8 and 22...exd3 blunder material, and afraid you are losing after that.
Game Analysis

Thanks Twomove, very helpful.
For 20 I was concerned about a possible fork on my rooks, although I see your point clearly.
I still think that at 22 to merely keep my pawn on the E file would leave me the same problem as I had in the end, which is how to take advantge of the passed pawn.
I think white got a clearer win with 31. Qxf4. I think that the knight/rook exchange that white garnered earlier in the game created the material imbalance, but white had to prove it decisive, which he later did. I also believe that a bishop is stronger than a rook if and only if the bishop has more pawns than the rook. If the pawn count is even, then the rook is winning.
11...bxc6 I think better was 11...Bxc6, keeping the pawn structure intact.
Some of white's play created your problems, rather than you made a key error. For instance, 16. f4 was a good play for white, and your response was good to take that pawn on the very next move, but once you did that, you ended up with 3 pawn islands. The fewer the pawn islands, the better the pawn structure. Overall, I think your opponent's understanding on how to attack pawn weaknesses won out.
Ironically, I thought white's last move was incorrect(better was Qd5), but that's a moot point.

That's fair comment pitbull, I definitely have to work on how I approach the game with regards to pawns.

Thanks.
I was 1379 when we started the game. I had lost a few games before my holidays as I was mentally exhausted, my excuse anyway , and am just getting going again. I am currently 1460 odd and reckon on this site I am about a low 1500, but am trying to improve.

Yes, think tonydal was right, was too quick to do away with black's position after 21Nxc6. After 21...Qc5 22Qxc7? Bd5 wins for black, because e7 covered.
Maybe 20...Qc3 was better than 20...rbe8 intending rb4 which would have made so sort of point of b7xc6 in first place.
Instead, of 22...exd3, finding hard to suggest a better move because if say 22...Qd7 23QxQ Bxd7 you are a pawn down anyway.

The consensus seems to be death by attrition leading to a weal position?
But does that mean, I should have been more aggressive earlier on in the game?

Hello,
A move like 11 ...pxc6 has to be followed up a lot more actively than you did in the game, because you are banking on two bishops and dynamic play to compensate for bad pawn structure. In fact just noticed have played Rb8, so can't play 11...Bxc6 because 12Bxa7 drops a pawn. 11Bxc6 makes a lot more sense now... lol. Oh dear I played through the game much too quickly the first time .
This is a game that I finished recently. I was playing black against a much stronger opponent and felt that I played fairly well, even having the advantage at one stage.
Alas, I was unable to convert and was soundly beaten in the end, perhaps because I should have tried to play for a draw near the end.
I would love for some feedback on this game as well as some suggestions as to where I could have done better.
Many thanks.