Megaflo electric terminal issue

[condor]

My Megaflow D70 is 11 years old now and approx every 2 years since new has needed me to replace the 11 inch long thermostat rod.
This latest time the thermostat blowing seems to have destroyed the spade terminal that is attached to the Immersion heater. I need to replace the terminal as the thermostat rod's pin can't connect to it.
Is it simply me crimping a suitable female spade terminal to the immersion heater a fix? or should it be a proper electrician that I get to fix it?
I'm also concerned as to why the fuse didn't trip out in the fuse box as presumably if it had then the damage wouldn't have been so bad.
Thanks