The overall transaction value of luxury homes in prime central London locations has fallen by over 20 percent, according to a U.K. estate agent, signaling that a correction in the capital's booming housing market could be afoot.

The data, collected by high-end estate agent Strutt and Parker, showed that the overall value of properties transacted was down 21.1 percent in the third quarter of 2014, compared with the same period in 2013.