Amazing David, timing is good with frosts imminent next week. Your raised beds may be gone, now you have something more elaborate! I wonder if the tree has enough light?
As for hotbeds, the heat fades after six weeks to a lower level for another six weeks or so. Probably enough for the tree all winter in view of your insulation.
Anyone reading this and planning a hotbed for propagation next spring, a good time to make one is early February, in greenhouse or tunnel preferably, then replace ingredients with new manure in third week of March approx, to have steady heat from early Feb to late April, the main plant-raising period, and less after that, still useful.