This seems like a good deal on T11 plugs on e-bay
http://cgi.ebay.co.uk/Mazda-RX7-2-6-FD1-FD3-NGK-Spark-Plugs-BUR9EQ-x-4_W0QQitemZ230100654017QQihZ013QQcategoryZ52640QQrdZ1QQssPageNameZWD1VQQcmdZViewItem
£31.99 for 4 plugs +3.99p&p not unless you know better:Thumbsup!