The canal's purpose seems a little unclear to me
I too grew up in Heston. What is now the Convent Way estate (just south of Wentworth Road) and the adjacent golf course were built on an old rubbish tip. There are various methane venting flues positioned all around the golf course. I remember this area catching fire (summer of 1976??).
I would suggest that the canal branch was originally built to move bricks out of this area to central London it was then back filled with general household refuse. This was a common practice and dated from the 1900's. There is a similar site adjacent to the canal at West Drayton.