Thanks folks, looks like I did the right thing to post here given the quick and thorough response!
To clarify, whilst my primary thought was to identify the location any other information about the boat, company, date etc is much appreciated. As far as the date goes, my dating was very much an estimate. It's a lantern slide which in itself makes it quite difficult to date (compared say to earlier carte de visite etc) and there are no fashion clues, which is the other thing that I can typically date images by. If people have a better idea, even if it's just a gut feeling, then do shout!
Interesting comment re: Brentford. I live in Hanwell, have an allotment practically next to the Grand Union at the bottom of the Hanwell flight, and in the summer months used to cycle down the tow path to Brentford when I worked in Kew. I did wonder if that wall to the far right might be the wall of the old Hanwell Asylum but I don't feel that it is. For reference here are a few pictures of my own taken along that stretch. Should anyone be interested here are a few of my own photographs from along there - http://www.flickr.com/photos/whatsthatpicture/tags/grandunioncanal/
We posted our comments at the same time. So it is Brentford? I shall have to pop down there and have a look. Thanks