As D8veh says, the load volume is key here, this will dictate, trike, longtail or low slung two wheel cargo. We have a cargo bike (veloelectrique.co.uk). That we use for loads of stuff... no pun intended. Seems to cope with as much weight as we can get in it, yet still a comfortable ride. You will probably find the electric assist is useful to get you started then you will just cruise along with minimal power as you'll find with British roads you are restricted by your bravery rather than the available power. I do see a few of the two wheel cargo bikes our way too, but never see them loaded.
John