2013.00 (Q4 2012) and 2013.25 (Q1 2013) data

Added data which has since been published by Nationwide  
* 2013.00 (Q4 2012) 
* 2013.25 (Q1 2013)

Source: http://www.nationwide.co.uk/NR/rdonlyres/4A05043E-454D-48E1-A732-58B345337078/0/UK_house_price_since_1952.xls