If you live/ride past Little Venice, Islington top lock (I can't remember it's real name but nearest the tunnel) or Victoria Park, there are taps for hoses there. Bring a hose and connectors or ask a friendly boater. Boaters are much more friendly to cyclists who realise the towpath is like a pavement with bikes on it rather than a road without cars.
If you live/ride past Little Venice, Islington top lock (I can't remember it's real name but nearest the tunnel) or Victoria Park, there are taps for hoses there. Bring a hose and connectors or ask a friendly boater. Boaters are much more friendly to cyclists who realise the towpath is like a pavement with bikes on it rather than a road without cars.