Made the oopsie batter with 1/2 tsp of garlic powder intead of the splenda . Made 4 small rolls and put the rest into a lined loaf tin, cooked it on 130c for 30 minutes and it turned out great. I split it (very carefully with a serated knife), spread the inside with tuna, mayo and cheese and put it in the grill and voila!!! Oh yeah, I buttered the outside of the roll before grilling, just like you do with a toastie.
I would have liked to cook it for a little longer but my grill blew up!!!! Sparks flew, bangs....banged and the trip switch...errr....tripped! So even though I really enjoyed my tuna melt, I don't think I'll be making it again soon! :-(