I'm one of those of those early sowers but I would have to agree it's probably too early to start bedding plants. It really does depend on where you live and the weather condtions and it is only February so we can all be struck with cold, snow and hard frosts. I wouldn't bother with the cost of heating a greenhouse.
Having said that I've geminated lobelia indoors and are now in the cold frame as an experiment. They were free seeds so nothing lost if they fail 