Remaps are often not about significantly increasing the top-end power, but changing the shape of the power and torque curves to suit the intended use of the car.
A normal road car, such as your mondeo, will be tuned to suit the average road driver - it will idle nicely at rest, and pull fairly smoothly through the lower end of the range, and will be fairly frugal with fuel. A competition car, on the other hand, will have a different set of requirements - they won't be concerned with idling or economy, so will tune it to get the best acceleration possible - matching the torque curve to the gearset as much as possible.
A lot of it therefore depends on what you want by 'quicker' - making a car get a better time over a quarter mile at your local drag strip is very different from cutting a few seconds off your lap time at Spa, or a forest stage...
I'd agree with jzd, think about the balance. If you're after a fast road car, tyres, brakes and suspension bushes make far more difference than small power increases. For that matter, so does getting a bit of professional driver training (which has the added advantage of being fun!)