Black To Play - What Should The Result Be?

FROM round four of the 50+ seniors at the British Chess Championships in Torquay.

Black to make his 43rd move in Spanton (1900/168) - Richard J Webster (1967/178)

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Black has three pawns for the exchange, including a passed pawn. Two of Black's pawns are doubled, but both white pawns are isolated.
I thought I was in trouble, but the position is drawn, although RW gives it his best shot.
43...a4+!? 44.Kxa4 Nxc4 45.Kb3
Not 45.Rxe4?? b5+!, and White loses the rook after 46.Kxb5 Nd6+ or 46.Kb3 Nd2+.
45...Nd6 46.a4 Kc6 47.Re5 Kd7 48.Kc3 Kc6 49.Kb3
The knight is tied to the e pawn, and Black's king cannot get out of its queenside corner.
The remaining moves were:
49...b5 50.axb5+ Kxb5 ½–½