some thoughts on power
The problem is that if you want a 650W microwave, for example, it's gonna consume at least - well - 650W!
If you're running that from a 12v supply it's going to draw at least 60-odd Amps in operation. Now, unless your microwave is within a meter or so of the battery you're going to loose a lot of voltage in the cable. Not to mention flattening your battery pretty quickly!
Basically you need mains, either from an inverter, generator or external hookup. If using an inverter keep it close to the battery, and let the mains cable carry the power the bulk of the distance.
We have a 800W Breville that we bought from Tescos for £45. It runs fine from any hookup we've tried - just don't use your hairdryer, hoover, etc at the same time.
If you want to run from a generator, then you'll need one that can handle it. We have a Honda EU20i (rated at 1600W continuous, 2000W peak) and that copes just fine. Being an 'inverter' type generator that adjusts its speed according to the load, it does 'sag' a little when the heating starts. You can avoid this by selecting the full speed mode (hare symbol)
Remember that power drop in wire is proportional to the square of the current being carried. 12V systems require 240/12=20 times the current of their mains equivalent (for the same power) That means the power loss in 12V cable is about 20*20=4000 times that of the same cable carrying mains!!
Hmm, probably said enough for the moment!