There CT stands for current transformer.
Basically for meters up to around 100A they are usually directly connected, i.e. the current passes through the meter to be measured, and that along with the measured voltage gives power, and then power integrated over time gives you energy (i.e. kWh).
For example, 10A at 230V = 10 * 230 = 2300W = 2.3kW, after 24 hours of constant use that is 24 * 2.3 = 55.2 kWh
However, above 100A it becomes impractical to route big cables via the meter so normally what is done is a current transformer passes a known fraction of the current to the meter for measurement, and the meter then knows to multiply by 100 or whatever the CT ratio is in order to get the real power.
This is normal for every big installation, and I guess these days the half-hour billing meter is also a standard requirement from the DNO. The catch is you might have time-of-day costs applied!
However, aside for the little details of how the metering is done, I have to agree with @Rockingit that you should engage someone you trust who has experience in this sort of thing to help from very start.
I would also say that if you are treating this as one building / system you really should look in to the heating and provision of hot water for showers, etc, as the use of heat-pumps and lower-rate heating of stored water could make a BIG difference to your electricity bill, and over a few years more than pay off the costs at the start!
