I use a variety of cheeses, what ever is lurking in the fridge usually use a mix of broccoli and cauliflower as I hit white food too. A bit of crispy bacon sprinkled over theveg before the sauce, made with mustard and chilli, then finished with a cheesy crumb topping.
Made like that it's a meal on its own. However if serving as a side I'd side with the pork/sausage suggestions.
Lots of mustard powder and Worcester sauce in the cheese sauce then topped with cheese and grilled to a brown crust. We had it the other night with a thick slice of gammon, lovely.