I would have thought you can't replace grill without the bumper.
New bumper will be £300-£400.
It will likely only come in certain colours, so may have to primed and painted at a body shop; another £200.
Fitting & Labour £200-£300
Tops £900 all in. That may on the heavy side; but your cars 4 days old, I would want the best on it.
I would take to garage to double check radar hasn't been damaged. I know you said it's working, but complicated bits of kit. Let them plug it into the laptop just to double check.