Diplomat was a brand name used exclusively I believe by MFI now in administration - or perhaps even wound up.
Speg and Hygena and probably others made badged appliances for MFI but that is of little consequence.
Here's a link from this site about how to discover if you have any warranty cover...
http://www.howtomendit.com/answers.php?id=226492
Good luck...
Peccavi
April 2009