Have no idea who Peter Grant the football player is, if that comforts you - and I watch a lot of sports. Do the Google search, that's what I do with my character's names; make sure that their made up last names aren't slang for explicit words etc. (but then again, I am very paranoid). I don't think it matters too much - I've come across hundreds of characters with the same names, but because they weren't the same character, I wasn't confused or annoyed. Nothing came to mind when I saw the name Peter Grant; and remember, he's your Peter Grant. There could be thousands of other Peter Grants in novels, but this is your Peter Grant, you know what I mean? As long as he's not a footballer, that is... hehehe. ... hope I've helped, by the way.
It won't matter if your character has the exact name with someone. I don't even know who that Peter Grant is. There are lots of books which characters' names are the same with other people. And this is your story. (I agree with AJ -- it's your Peter Grant.) It's your way of writing the story, and the name won't even matter at all.
Never heard of Peter Grant, and it's ok to have the same name in any case - I found a real life Jack Reacher on Facebook and Lee Child's bestselling series is the Reacher (yes, Jack Reacher) series. Does anyone care? Nope. However Peter Grant sounds exceedingly ordinary...
About the same-name-as-an-existing-person issue: I have two points to make: 1. There's a difference with if the real person in question is famous or not. 2. There's an even much larger difference between taking an existing person's names and copying them over as the name of one of your characters and just happening to use that (combination of) name(s) by coincidence. Personally I take care not to directly copy names off of real people, or fictional characters for that matter, that I KNOW OF. I DON'T CARE about ones I don't in a sense. I often do google searches and the like for my characters' names, but for (slightly) different reasons. I take names from both people I know and famous people frequently. After all you DO need to have your names from SOMEWHERE (unless you invent new ones, as I occationally do). I think I even do this more, in a sense, that most writers. I like taking names from 1. people whose names I like, 2. people I like, 3. people who have physical and/or personality-based likenesses with my characters, and I might even do 4. use names of people I don't like as names of fictional villains. The point is that I don't take all the names of these people all at once; I use a few, one or part of one name of a real person and join that together with something else to make a full name of a character. The only real place in which I can see this really becoming an issue is if you're taking a mononymous person's name and using it for a mononymous character's name (but this is unlikely to happen and has a myriad ofpossible solutions). I currently have over 200 characters. I need my names from somewhere. But I do, in my opinion, choose wisely. To finish off: You decide whether you like your character's name based on all factors combined. If you're fine with your protagonist bearing the name Adolf Hitler then that's your choice. Of course, in certain situations, you might be ... frowned upon ... for using a real person's name for one of your own characters; usually in situations where those real people believe themselves to suffer from your work, but again that only happens if it's deliberate on your part. - Bjørnar