Preheat the grill.
Heat a little oil in a medium, non-stick frying pan (approx. 24 cm). Add the onion and bacon and cook for about 5 minutes over a medium heat. Cut the potatoes into cubes about 1 cm thick. Add a little more oil to the pan then add in the potatoes. Allow to cook for another 5 minutes, stirring frequently. Stir through about half the spinach.
In a bowl beat the eggs, then stir in half the cheese, the rest of the spinach and a little salt and black pepper.
Add the egg mixture to the pan. Move the pan around to let the egg mixture run in under the potatoes and get to the bottom of the pan. Sprinkle over the remaining cheese. Turn the heat to low, then cook for about 10 minutes until nearly set. Place under a medium grill, and cook for about another 10 minutes until the top is set and golden.
Slice into wedges and serve with a green salad and bread.