Try Henderson's Vision and Image in Early Christian England.Cambridge,
1999. There is a brief discussion about the use of Romulus and Remus
in Anglo-Saxon art. I believe that, in the later Middle Ages, it
was fairly common practice for histories of dynasties or countries to trace
their roots back to Rome or even to the Garden of Eden to secure their
pedigrees. Sorry, this is a little late for me but I would look at
manuscripts.
nb