Having had the opportunity to scrutinise the instructors' briefing notes for one of these Ferrari experiences and helped a driver I have managed through the process of becoming an ARDS Licensed Instructor these would be my tips for getting the most out of the experience.
Instructors will be of all ages from seasoned pros to young up and coming drivers. Remember even if your instructor 'looks like a child' he or she will be an experienced racing driver. He/she will as a minimum hold a National A Race License and that license must have at least 10 signatures from at least two different circuits before they can even apply to be an instructor.
Silverstone also prefer their instructors to have at least two seasons experience in a National level championship (i.e. club racing does not qualify).
The instructor will then have completed the ARDS instructors course and passed the assessment at the end (not everyone passes by any means). The circuit they are affiliated to will then recommend to the MSA that the instructor is granted a license and recommend the Grade of the License. Grades start at Grade D and run through C, B, A through to Grade S. A new instructor that does well in the assessment may skip Grade D, straight to Grade C but no higher and a Grade C License is the minimum requirement to actually instruct one to one on track.
The other thing to remember at Silverstone is that they operate a ZERO TOLERANCE policy with regard to spins and this applies to both the customers AND the instructors. Therefore your instructor will be ensuring you get nowhere near the point where this could happen.
The instructor will likely have instructed many customers of varying level of experience and or skill. They have a very short time to make a judgement on how quickly they think they should let you drive the car when it is your turn. If you make them nervous either by your attitude or the way you drive they will keep your speed down as they will firstly have regard for your and their own safety and remember if they let you overdrive and it all goes wrong their job is also on the line.
I would suggest not getting in the car with the attitude 'I'll show them what I can do' rather listen to them and build up slowly giving them confidence that you are listening to them and so they can also decide whether or not they 'trust' your driving.
To give you an example of how much you should measure your own driving keep this in mind; When they give you the fast passenger lap at the end of the experience they are instructed to drive at 7/10 ths and their brief is "The lap should be driven to demonstrate a smooth, controlled high-speed technique and NOT the ultimate ability of the instructor."
Whilst all this might seem to some downbeat the instructors are also briefed that they should ensure the customer does not feel 'short changed' so they will be doing everything they can to ensure you enjoy the experience without compromising your safety or their continued employment.
HTH Robin