Question re. bleeding radiator and pressure

Hi all.

Firstly, thanks Mike, great forum and website.

I have just moved into my flat and excited being a first time buyer!

I am so far impressed by the speed of heat and hot water from this boiler.

My Electramate 2000 comes with a expansion vessel on top of the boiler (do they all?) and unfortunately I don't really understand the system.

I noticed that my radiators are cold at the top and hot in the bottom and have just bled the air out. I have then subsequently read that the system is a "sealed heating" system, does this mean it is a no loss system? One of my radiator has lost quite a lot of water due to last owner leaving the lockshield valve out without me knowing (grrr). Does this means I have to refill it with water?

The pressure on the boioler runs at around 1 - 1.25 bar - is this normal?

Many Thanks,
Adam

Another quick question - should the boiler only make a noise when it is heating up.

So, it shouldn't make a noise (ie complete silence) when radiator is not on, hot water not used and boiler not heating up?

Would anyone be able to explain to me how the boiler know when to use economy 10 times? I have read other posts and mine has a large red button (kitchen type lever) and a smaller white switch (light switch type). I was told by EDF I have an economy 10 meter but there is only 1 reading??

Many Thanks
Adam