That was one thought that occured to me, Ernest. However, although small, these boats were considered very seaworthy, they could be handled in seas that would give larger vessels problems, and their movements would not be restricted to the Thames estuary. Google reveals that in World War Two a large number of Bawley boats joined the flotilla of small craft that assisted in the Evacuation of Dunkirk (maybe forty or fifty miles across the English Channel?) Here in Fleetwood, Morecambe Bay prawners would be the regional equivalent of Bawley boats. In their day they could readily manage a trip to the Isle of Man or even Ireland. And if you think the Irish Sea might be relatively sheltered, check out the fate of the Riverdance in February of this year:-
http://www.trekearth.com/gallery/photo831691.htm
(After fruitless attempts to refloat her, the vessel was cut up on the sands. Demolition is almost completed).

Ross