Yes, it is that model, it is place relatively low, and yes again you are correct that the electrical part of it is place under the wash basin. The control unit, pump and dial are placed in the shower cubicle, but relatively low.
In terms of the misquote that you mentioned of the water company. This implies than that because both the power shower and the WC etc all feed of the same pipe of the water tank, I cannot that easily cap it off and feed it from the mains, since my power shower would then feed of the mains as well. You can visit Plummer
for more info.