Two storey extension over carport

We're looking to build a 2 storey extension to the side of our house which will consist of a bedroom with ensuite on the upper floor with a carport underneath. The upper floor will be about 28 square metres.

I know the build costs can vary greatly depending on different factors, but if we were to estimate that it was going to cost £1000 per square metre per floor, how much more than the £28000 would we be looking at taking the car port into consideration? I presume the cost would increase somewhat as we would need to "build up" to the second floor?

I'm not sure i get the question?

You say you are building an extension consisting of a car port with a room above, i get that bit.

It's the "take the car port into consideration" i'm not getting.

Do you mean building it as a standard two storey extension, i.e. a furnished room below as opposed to a car port?

No, there's nothing below except the car port.

Its only the one floor we're extending, but its the upper floor as opposed to the ground floor, so we're going to have an elevated extension with the driveway still underneath. What I'm wondering is how much more expensive would it be do do it this way as opposed to extending the ground floor.

It's obviously going to have the same floor space either way, but I presume there will be additional labour and material costs involved in building it the way we are proposing.