Don't you just press the "DISP" button, located to the left of the viewfinder?

That's how I would do it with my Powershot.

Pressing the disp button just brings up a menu of options, none of which look like being the right one! I'm sure it is simple enough, but I just haven't figured it out yet and it's annoying me!

You need to enable the liveview shooting option

so that I can't use the screen as the viewfinder

why would you want to ?

Apparently needs to be in creative mode before the liveview option is available. Sorted now thanks guys.

Simon - because I can.

Simon - because I can.

as you like, but an actual glass viewfinder seems way better than holding the thing at arms length to me...