Great diagram.
The conduit won't so through the gland to the outside of the tank. The conduit pushes into the bottom of the gland. I wrapped some PTFE tape around the conduit to make it a tight fit. The second gland is at the bottom of the conduit. Otherwise, you have the basic idea.
I was going to buy a couple of glands tomorrow (I need them for another project which has stalled at the moment) and set up a model and photograph it. My drawings are awful.
There are three wires in the float switch cable. They are brown, black and blue. ( You would connect the brown and black wires if your were connecting this up to a submersible pump.) The wires to be connected to fill the tank are brown and blue. Black isn't used. I used a 20 amp junction box to connect the wires up, similar to this
http://www.screwfix.com/p/20a-4-terminal-standard-junction-box-white/1239dUsing this meant I didn't have to cut the black cable.
I wired the + to the brown wire and the blue is the return to the solenoid (+), you would also connect your 230v booster pump's positive to the blue wire as well. So the solenoid and the booster pump switch on and then off at the same time. I have the supply from a normal 230 volt wall socket in the garage. I have the control to switch everything off at the plug if necessary.
I prefer to switch the positive on and off. It means that when the float switch switches the current off, the solenoid valve (in my case) is 'dead.' I also believe that its important to have an earth leakage/RCD at the plug - water and electricity don't make good bed fellows.
The length of the conduit is around 300mm. The length of cable from the pivot (bottom gland) will determine how full the IBC tank is when it switches off. I have left a gap of around 200mm when the water level is full. This means I have been able to add an overflow pipe onto the side of the IBC tank just in case there is an issue. This pipe (some 1/2" garden hose pipe) runs outside to the drain off the garage roof. In 7 years the system has been in operation, this overflow has worked once due to a self generated issue.
this float switch will kick the r/o on when I have taken around 150 liters from the IBC tank. I find this is fine as the longer the r/o works the better.