Selling homebrew temperature controllers

I'm wondering if anyone here has experience with meeting the standards for selling temperature controllers.

Basically my design is a portable appliance consisting of 2 PID temperature controllers for controlling HLT and boil kettle temperatures, a number of switches, relays, panel LED's and receptacles housed within a plastic enclosure.

So my understanding is that I must meet the requirements of regulation 80;
"Every new or used fitting, and every new or used appliance, that is sold, offered for sale, supplied, or offered for supply must be electrically safe."
And that the compliance is NZS 3820, which is fairly easy to meet.

But I need evidence to prove my appliance meets NZS 3820. But it seems that the only way I can prove this compliance is by a lab test, which is going to be quite cost prohibitive (unless my tested controller is allowed to be used as a sample for any other controllers I ever make of the same design).

So long story short, does anyone know of any other tests/certification I can use to prove compliance that isn't going to break the bank or land me with a large fine from the regulatory authority?