Hi Peter,
of course I was being flippant by suggesting Irene Handl, although she does typify Englishness for me. However your suggestion of Silbury seems even more bizarre. As we are well aware, virtually no one in England knows anything about Silbury. If you must have a megalithic icon then it would have to be Stonehenge as it's probably the only Megalithic monument that most English people have heard.
A more serious suggestion from me would be a picture of an English high street showing curry houses, chinese takeaways, kebab & pizza shops, chippies, irish pubs etc, an image of our wonderful and ever changing multi cultural hot pot.