Hi Gina - I'm having trouble understanding why you would want a 50mm f/1.4 if you already have the 1.8 version.
Unlike the others in this thread I think it is entirely reasonable to want to have a zoom lens. The obvious choice is a 10x or thereabouts superzoom for convenience and for avoiding missed photo opportunities. Unfortunately, you have a 5D Mark II which is full frame so you can't use EF-S lenses and there are lots of superzooms from Canon and independents for EF-S mount Canons.
Canon does do a 28-300, but it's an L-series monster and not only is it big and heavy, it's expensive (£3K). I don't think there are any affordable superzooms for full frame Canons
But fear not, I think the lens for you is the Canon EF 28-135mm f/3.5-5.6 IS USM. It's relatively affordable (around £375 from non-grey dealers and even cheaper second hand) and although it's not a luxury build by any means, it's a decent optical performer. Some even rate it over the much more expensive EF 24-105 f/4 because of its design usability (nicer zoom action and bigger control rings).
The 28-135 zoom range means you get a very usable wide angle all the way through standard and portrait focal lengths. As you have a full frame camera you should be able to get good defocused backgrounds even at f/5.6 at the long end of the zoom.
The lens is also physically light and relatively compact.
Well worth considering in my book.
PS I have to say I did scratch my head a little about your choice of the 5D Mark II. Without going into personal reasons I would have thought a big heavy 5D Mark II (and quite expensive) with big heavy lenses would have been far from your short list of cameras!