I repaired my heated jets this afternoon. As with yours Mike, the wires had corroded and broken off.
1st disconnect the electrical plug a bit further back attached to the bonnet in a plastic support. Then if you tug on the plastic connection for the water pipe on the jets, a section of the heated jet comes out.
You should have two metal strips on either side of the plastic pipe connection. These just slide forward (away from the pipe connection). All you are then left with is a small piece of wire terminated at one end with a black plastic plug and (if it were intact) 2 small thin 'U' shaped metal contacts.
I cleaned off any corrosion with sandpaper, stripped back a little of the broken cable and then soldered the broken wires back on. A small bit of insolation tape to cover and bare wire then refitted it.
Approx 30 mins work and thats only because it took so long to clean the connections up.
Hope this helps
Tattie