fill the roundabout with mass plantings. As the view on approach is focused on that fountain, height would only hide it, however it is important on a large scale to play on dimensions of height aswell as depth. So I would plant out the rear of the fountain with a semi circular arrangement of tall plantings, perhaps even trees. Something with delicate foliage like that of a birch grove, so light and perspective can still be seen through them.
In from of that a dense planting of hostas wi plenty of foliage variations, height and colour. I would add another urn and topiaried buxus on your garage wall in between each door to match the one visible next to your porch. Repetition and symmetry is an important design element in formal gardens.
I would consider balancing the structure with the garden, as it is sparse, and landscaping with much open space will be difficult to achieve a dramatic effect without it.
I would have a builder quote to construct a post and beam addition to the front of the garage, bringing out substantial timber rafters out from the wall about a meter, with heavy posts, perhaps even pillars, this would be ideal to paint In a white trim, reminiscent of country estate homes, and provide a gorgeous arbor to plant a white hanging wisteria for example. Draping white blooms from this in spring and summer would look divine, and lighting would further enhance both the fountain garden and the new arbor.
Good luck.

Thankyou for your ideas. The photo does not show all the front of the house. it is quite large. we have two pots and urns on porch which you can see as you drive up and also another one on the other side of the front of the house..and also two large urns (the ones with lids) on pedestals at the start of the driveway.
we also have large gardens either side of the driveway/island garden and these have large trees in them. so i fear putting more trees in would close the front in to much and crowd it out.

For the development of sage advice, you need to show the entire picture you describe in words above, give your advisers the full picture to consider, before offering advice on the center or the roundabout, keeping it all in proper context, the view from the street as well as the views from within the home, should be considered. Have fun with it. You have gone bold, so you need to have it blend with all the other spaces in view. Enjoy the journey.