Gosh, at the risk of sounding very very snobby I'd say there are an awful lot of middle class, affluent schools represented in this thread.
At the school I teach in now (medium sized independent in the home counties) the most common multiples are:
Frederick, Sebastian, Max, Jack, Christopher, Hugh, William, George, Harry, Hugo, James, Charles, Joseph, Joshua, Thomas, Oliver
Annabelle, Georgina, Georgia, Alice, Grace, Jessica, Isabel/la, Mia, Harriet, Elizabeth, Abigail.
At the last school I taught at (small primary in the North East, 4 years ago) the most common multiples were:
Declan, Dylan, Damon, Callum, Reece,
Chelsea, Kelsey, Holly, Jamie-Lee, Amy