Although there is pictorial evidence, (as Craig has mentioned) throughout the 14th, 15th and 16th centuries depicting bows used in batlle with recurve tips I think it's fair to say that it should be viewed with a degree of caution. But, what we have to remember is, Britain was not an isolated society. Before the battles of the hundred years war, there had been over two hundred years of tooing and frowing, back and forth to the Holy land. It would be easy to see how eastern bow characteristics were incorporated into the more traditional longbow designs of western europe.