Forgive me for being dim here, but I still don't really have an answer to my own question.
I do understand about leaving the computer on or off, as far as the console and monitor goes... but I still don't understand if I should unplug the whole thing from the wall socket when I'm not planning on using it again for the day.
In England, where I'm living, there are on/off switches that can be switched right at the wall itself. When it's on, I assume there is still some power going to the computer, and that's my question... is it better to shut the whole thing down-ie, no power going anywhere- than just turning everything off but leaving it plugged to a live electric line? I leave my TV plugged in with the wall switch on, (but it's completely turned off at the set), along with my answer machine, washing machine, radio, etc, but I want to establish if this practice shortens the life of the computer, or is any way worse for it? SO sorry this is long-winded! Thanks!

Very few on/off switches on electronic equipment actually turn the power on and off. Usually that is done by relay. The on/off switch controls the relay. The relay can also be operated by software. Do you usually go to the start menu and select power off when you shut down your computer? When the computer is shut down, as long as it is still connected to electric lines, the circuits that supply power to to the on switch and the relay are still drawing current. The current is very small, not enough to make any difference on your electric bill.

I don't know how good your power is. One advantage of disconnection from the power line completely is that it gives complete protection from power surges from switching large currents elsewhere of electrical storms. Since I added an uninterruptable power supply last summer plugged into my surge protector, I continue my computer work through electrical storms believing no power surge will make it through. If you don't have a surge protector, and do have power surges, you are better off unpluging it. If you do have a surge protector, unplugging it protects it from a surge it can't handle.

Some people argue that leaving the power on makes the computer last longer. No matter whether you leave it on or off, likely it will still be working fine when progress requires an upgrade. Even if you don't want to spend the money for the very latest, so many other people do that your computer can no longer handle all the new formats and upgrades when you try to work with others.

Another thing. In the United States our power has one wire at 115 volts and one wire grounded. The wall switches only break the connection for the 115 volts. A nearby lighting strike could send a surge through the grounded wire to a computer connected to a turned off wall switch. I think you use higher voltage in England, but I don't know how your switches are wired. If they are not 2 pole switches, breaking both sides of the circuit, you would need to unplug it to completely isolate it from the power line. That might be over doing it except during a storm.