Finally got a bit more information. The trip was in 1963 and my parents didn't navigate into Stratford, it hadn't been 'cleaned out', they got a train from somewhere adjacent!
The boat however was a BW one and called 'Water Vole' and definately went from Gas street basin. As fare as I can tell, mainly from previous threads on this forum, Water Vole was/is Kelso and was cut down by BW in the late 1950's.
There are about 15 pictures on slides which when I get to see them (they are on loan) I will hopefully scan and see if there are any identifying features of both the canals and the boat.
Regards