LONDON, England (CNN) -- Elton John and his partner David Furnish are among hundreds of gay couples in England and Wales making legal history as they "tie the knot" on Wednesday. The couple are exchanging vows during a civil partnership ceremony at Windsor's town hall -- the Guildhall -- where Prince Charles and Camilla Parker Bowles wed in April. The couple plan a low-key private ceremony, with only John's mother and stepfather and Furnish's parents attending. Later in the day, the couple will throw a star-studded party, costing an estimated $1.75 million, according to The Associated Press. Two giant white...