it get a bit messy towards the river around brentford, a few steps to climb and a few bridges to cross the thames, some old warehouses you have to ride through etc, but a mile from the thames it goes to proper canal path and is a decent surface for a few miles / as far as the t-junction where you choose if you want to go to central london or birmingham
as far as i recall it get a bit muddy once you leave the M25 heading nw ish but you can probably take a section of that canal way towards west drayton
it get a bit messy towards the river around brentford, a few steps to climb and a few bridges to cross the thames, some old warehouses you have to ride through etc, but a mile from the thames it goes to proper canal path and is a decent surface for a few miles / as far as the t-junction where you choose if you want to go to central london or birmingham
as far as i recall it get a bit muddy once you leave the M25 heading nw ish but you can probably take a section of that canal way towards west drayton