Yes. Its the flush cone leaking. There are 2 types- Internal or Externeal. One pushes into the pan and one seals around the pan. You can get an internal one here:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=200262169707&ssPageName=STRK:MESE:IT
Blackpool Boiler Spares, October 2008