My Hygena fitted electric cooker blew?

Hi,
Our hygena fitted electric fitted oven and hob.....
Well,whilst heating up the oven yesterday morning the electric went off in the house,(stormy weather here?)
I switched the mains circuit switcher back on,kettle and oven working,BUT the oven was not getting any hotter.....hob works and even fan and light and some warmth in the oven but no where near proper temperature....,cant be main fuse/appliance fuse as its still working....has a Thermostate or something BLOWN....HELP....or can you tell me how I can track down a good service agent....we didnt buy the cooker was here when we bought house last summer etc...
Any advice gratefully received,Paul.Canterbury.