Is it just the size of fuse you want to know which should be in the plug top of the hob?
If so then its just a 5 amp fuse that should be fitted into the plug top.
The hob ignition is supplied thru a fused wall switch which houses a pull out fuse drawer, & is fed from a modern trip switch panel The first fuse was replaced with a 3 amp which promptly blew both fuse & trip. Replaced with a 5 amp fuse but with same result. Suspect ignition unit has failed & is shorting circuits. Is this your opinion, meaning that a replacement part will be required.? The hob has been in service for 15+ years, so maybe time for hob replacement !!