Installation of Inverter, battery charger etc

Guess it depends on type of camper trailer you have mate. With mine, there is a dedicated compartment for a couple of batteries and i have whacked a largish 3 stage 15 amp charger in there too. I don't have an inverter in the camper, but the one in the 4x4 is mounted onto the cargo barrier, above the head of the rear passenger.
If you have a camper without any small compartments, I would suggest you consider placing such items securely inside one of those hard, black plastic battery storgage boxes with a secureable lid. I would bolt both items to the "walls" of the box and then bolt the box to the camper (once again it depends on the type of camper you have.
Hope it works out okay for you...

If it's any kind of half decent interverter you will probally be best mounting it inside the vehicle so that you can hook it direct to a battery in the front of the car via 8g minimum cable.

I have a 420w Pure Sinewave inverter and it draws up to 45amps continuous if loaded up. With that kind of current draw you want your motor going and accessories off so that the vehicle can handle battery charging and running the inverter. Of course you are not neccessarily going to be using that kind of draw on it all the time, but if you've spend the money you might as well hook it up in such a way so that you can take full advantage of it if need be.

My inverter will run the entire lounge room (Set Top Box, Amp, Sub, Mast Head Amplifier, 109cm TV, DVD, 75w Lamp and Pedistal Fan) if I want it to. (have done so in power failures). The surf can hold that up at standard low idle. Handy to have.