10 More Minutes / 10 Minutes Left?

I think both are fine, it's just that the word "more" should be in the end:

We have 10 minutes more.

We have 10 minutes left.

300 on "have five more minutes"
http://books.google.com/books?q=%22have+five+more+minutes%22&btnG=Search+Books

450 on "have five minutes left"
http://books.google.com/books?q=%22have+five+minutes+left%22&btnG=Search+Books

thus both are used in books on a comparable basis.

Although you can use either, there can be a slight difference in what is emphaszed.

You have ten more minutes - emphasizes how much longer it will be.

You have ten minutes left - emphasizes how little time is left.

I can't wait for the work day to be over. Ugh. I have 30 more minutes.

You better hurry up on that essay. There are [only] 10 minutes left before you have to hand it in.

GG,

I have 10 more minutes

and

I have 10 minutes more -

are they both okay?

My American ear prefers "I have 10 more minutes" but I don't know that that is universal.

I vote for "10 more minutes" for this case. All the following sound about the same for me in the above situation.
You have 10 minutes.
You have 10 minutes left.
You have 10 more minutes.
However, "two minutes more" sounds more natural to me in the following case:
You need to cook it a bit longer.
How much longer?
Cook for two minutes more.
GG, what do you think?

Grammar Geek"I have 10 more minutes"

Or "I have 10 minutes left" both sound very wrong to me as isolated sentences. I would say:
"I only have 10 minutes left",
"I only have 10 more minutes",
or
"I have 10 minutes left until + sub-clause",
"I have 10 more minutes until + sub-clause".

Do these cookies look done to you?

No, I'd say they need to cook at least another two minutes.

No, I'd say that have to cook at least two more minutes.

No, but the timer says it's still two more minutes until they should be done.

Huevos, NONE of these work in isolated situations. You need to have a reason to say them. You wouldn't walk up to someone and say "I have ten more minutes." But if someone says "Excuse me, I think it's my turn to use the computer now" and you point to when you signed in, knowing you have 30-minutes slots, you certainly can say "I have ten more minutes."

EDITED to address the original question.

If I know we have to leave in ten minutes, and my husband is still in his jeans watching TV: Honey, there's only ten minutes left until we have to go. (I hope instead of arguing with her about grammar, you got your butt up and changed your clothes!)