Hi, I realize that this is an older thread, but thought that you might appreciate the info. I not sure of what you're looking for, but we recently got a hobby greenhouse and are still working on setting it up and getting electricity and water out to it so we can begin to winterize it. So I can't really help you out with the experience end of things but I can provide a couple resources here in Canada.
The one of which is right here in Ontario, called Backyard Greenhouses:
Greenhouse, Greenhouses, Greenhouse Accessories, Canada Greenhouse
And there is also BC Greenhouses:
Greenhouses | Largest selection in the United States and Canada
We ordered the greenhouse from Backyard but they shipped it from BCG since they didn’t have the one we wanted in stock, so you just have to keep the cost of freight in mind, but they do seem to have comparable pricing.
About the heating issue: it is a good idea to get the five wall poly since it conserves more heat therefore costing less. We also laid a double layer insulation on the flour over course gravel, then covered it with another couple inches of smaller gravel. So far I’m not getting any weeds and there seems to be very few bugs showing up. The insulated floor, absorbs heat during the day and releases it at night and in this way it costs less to heat it as well.
If your interested I can provide more info.