Morning Phleb, sorry to muddy the waters, but before you rush into anything I think its worth pointing out;
5sq m would be a very small drive.
The average parking space would be nearer 10sq m.
Did the builder say 5metres squared which,of course, is 25sq m. Ergo 5 times the cost.
Any chance you could go out with a tape measure & measure up for us.
Or pace it out. Long strides for a metre. :)