I have a Panasonic combination at home which I have been very happy with for the last fifteen years, my mother has one which she has been using for longer - I think the old ones are better (Panasonics, not mothers). I only use it for things like jacket spuds and warming pies, whether it would work for a souffle or Yorkshire pudd'n, I have no idea.
Microwaves do have a huge power draw - the listed power is the output power, not the input - so an 850w microwave will be drawing 16-1700w, and if you add a 1.5kw heating element on top of that, it might be a bit much even for shore-power in a marina. I love the convenience of a microwave, so for the camper I bought a low power version to work via a 1000w inverter (this one from Kitchenware Online) which I am very happy with - it's perfect for reheating a pasty, heating tinned vegetables, or warming a cup of soup with reduced washing up and faff!