How to stop Hotpoint electric cooker blowing trip switch?

My Nan bought a new cooker around 12-18 months ago. She had a pan of boiling water on it which overspilled and it seems some of the water made it down the crack at the edge of the glass hob and the side of the cooker. This caused it to stop working. Every time you turn the cooker on it flashes orange under the hob, has a bit of a bang and trips the fuseboard. She had a hotpint engineer out as it happened in her 12 month warranty, but he said it wasn't covered as water had overspilled. Sounds a bit unfair to me, but anyway. She's looking to buy a new cooker, but I'd much prefer to fix her old one. The previous engineer, took the back off, tilted the device and dried it out and it worked again. This time however I can see no water in the unit. Any ideas?