I think different areas have different bowel preps so I wouldn't take any of our experiences of taste/timings etc as what yours is going to be like. (I think mine was like Andrew's Liver salts, very fizzy, very sharp.)
You need to read the instructions given with the medication, NOT what the Dr said, and NOT what people say on here. (I wasn't allowed to drink anything but water, and would have been in trouble if I'd drunk black tea like the poster above suggested.)
So, yes, take it at 7am, well you haven't taken it, so take it now, and take the next one twelve hours from now.
The whole point is that your insides must be
a) empty
b) not dyed by any recently eaten foodstuffs.
If the 7am/7pm is a little early for the 11.30 appointment, it won't matter as your stomach will still be empty and in the right state for them to get a good look. What you want to avoid is any chance of taking it too late and there still being something in there.
The prep was OK, honestly. I had no tummy ache or anything. It was just like doing a wee from your bum TBH. Like a previous poster I was chuffed to read "bowel prep good" on my notes.
Re the colonoscopy itself, again it depends what hospital you are at. There was no gas and air when I had mine. I had painkilllers and sedation, although I did not feel sedated at all, I reckon I could have driven home. I didn't have any wind either. (With the gastroscopy a fortnight before I was as woozy as anything and had the most alarming wind!)
What I did find was that the "discomfort" 
occurs when they are pushing the colonoscope up inside you as far as it will go. They then withdraw it and that's when they have a look. That bit was OK.
Good luck!