Thank you Kent.
I was able to dislodge it with a giant set of pliers (I know, not ideal). The replacement part is to arrive Thu or Fri and when I go pick it up I'll request a 55mm hex nut.
I'll post pricing details for the electric resistance when I actually pay but over the phone I understood about €85, with taxes and shipping to the store.
---In amelyachtowners@..., <karkauai@...> wrote :
The heating element on the Quick Nautical Boiler B3 40L has a 55mm hex nut. You need a 55mm immersion box wrench to remove it. It's an axle nut wrench that you should be able to purchase at a Napa or other auto parts store.