The application fees (payable to your local authority) are currently £150.00 for extensions and £335 per new house.
This type of application is simple in comparison to the detailed application. You are effectively asking the council to approve the principle of whether you could build a property on a specific plot.
The applicant submits the relevant forms together with an ordinance survey plan with a red line outlining the plot.
Most of the time, an outline application will also be accompanied by layout plans and elevations to show how the property would fit with in the site, these drawings are for illustrative purposes only to show the council the potential of the site. If you would like the local authority to consider some of the details formally, you can state this on the forms issued by the planning department.