It should be a win as your bishops are the same color. I would start with f4 to limit his bishop's range and free my king then i would attempt to bully his bishop off the good diagonals unless he swaps and your better kingside pawns should win. You must "police" his king after the suggested f4, ie be careful of his marhing his king down and taking your kingside pawns. Should not be too difficult.
Draw?

The key question is to make your extra-pawn count. Here is my 2-pennies' worth. It is only a broad outline. Comments welcome!
If we assume that you will leave your Q-side pawns in light-squares, we should expect a pawn lock-up there (unless Black King is ready for a long walk across the board - which of course, you'll do your best to block or take advantage of).
On the K-side, you need to hamper Black's movement (both King & Bishop). A good way to do it would be 28. Be7. It will deny a good post for their Bishop to block your pawn-progress. It won't much do much to block their King, but might encourage a bit of detour by their King, chasing your Bishop. Meanwhile, you have to get your King towards g5, from where you can shepherd your f-pawn to the finish line. For this, you need to play 29. f4.
You could try to post your Bishop somewhere on your side too, but somehow I feel (?) it will be more effective at e7 (moving to d8 / f5 when chased).
That said, I tried my wits against a stronger opponent in an end-game and lost it after being 2-points ahead . So in your place, I would've taken the draw and counted myself lucky!

Well, you could have tried some risk-free continuation. Assuming that he draws if he brings his King to f5, you may try :
28.f4 (to free your king from the defence of g3) Kg6 29.Bf8!? Kf7 (29...Kf6 30.Ke3 g6 31.Ke4 and you have improved your position without taking any risk) 30.Bc5 g6 (30...Kf6 31.Bd4+) 31.Kf3 Kf6 32.Ke4 with a pull.
Is it winning ? I don't know : but it's worth a try
Thanks for the input people, I guess I probably should have played on, I think the worst I could really have got is a draw and there's would actually appear to be more chance of a draw than I first realised.

23 Bxf3 I would have given Nf6+ Isolated the pawn and then exf3... I thought White had better chances and Black was keen to get away with a draaw

It should be an easy win for White. march your pawns, exchange down to 1, fix his king in defense, then at the right time march your king West. 1-0

This is clearly a great position for white. I would never agree a draw here, because by playing on, you risk virtually nothing, and the defense is very difficult.
I think this is a pretty easy win for white. Here is a possible continuation:
f4 g6 Bc5 a6 Kf3 Kg7 g4 Kf6 Bd4+ Ke6 gxh5 gxh5 Ke4 Bd6 f5+ Kf7

Well, the title says it all, I accepted a draw offer from a strong opponent, I just wanted some thoughts as to whether it was a draw or anythng that was good or bad in the game, particularly any blunders that I made.
Any variations in the notes, I have added in the movelist in case what I have said isn't clear.