Hello Sharon
I don't know if you have looked at Graham Aircraft Hire's web site. It says all enquiries and bookings are handled by Props Away Ltd., and gives a name and contact number. However, I believe the information you require would not normally be made available to any one unless it was requested by law enforcement agencies such as the police, Special Branch etc. One of the main reasons people use non scheduled aircraft to travel is the privacy issue. They don't always want people to know where they are going or what they are doing. Operators of these aircraft will respect this and treat the required information as confidential. This confidentiality is part of the premium price their clients pay to use their services. There is also a security issue in releasing details of passenger lists and cargo manifests.
I may be wrong but you probably need the services of a private detective with good friends in HMRC and the UK Borders Agency.
I know it sounds a bit like Spooks but having been in the business I know what it's like trying to get what is often quite sensitive information.
Cheers
Rob