I'm not convinced bay trees will work with your current step since the front door is raised so high off the ground.
I'd also be reluctant to put a porch on the front as it will risk either obscuring the window above your front door or the feature lintel over and hence always look like a 'bolt-on'
I see what you mean about the garage, but I actually don't think it's too bad and I think there are cheaper/quicker things you could do to make a difference.
Is the front door in it's original position, or has it been brought forward?
Everything that follows is of course personal taste. You have already a very smart looking house.
To my mind, the entrance way is a little tall and narrow with nothing to break up the lines. It looks like you may have had a new front door fitted? If not, would you consider replacing it with one that had a letter box higher up? It helps break up the 'long thin' appearance of the entrance way.
Rather than bay trees - a light to the LHS of the door or a 'house number plaque' will give the front some interest. Hanging baskets would also inject some colour.
If you're getting the front landscaped, a larger (wider) step might also help (and would potentially allow the ubiquitous bay trees).
What's the white plastic fascia for above the garage door? Is there anything behind it? I agree with others who have said that a 'more traditional' (side hinged) set of doors would be more in-keeping with the house, but there is a practical down-side to these of course.
It's hard to tell because the photo was taken on an overcast day, but do you have any window dressings in your bay window? From the photo, the windows appear very black with a black front door and a black garage door. A sea of black. Could you put a chrome handle on the garage door?
Alternatively would you consider repainting your garage door/front door? A dark green would lift it a little maybe?