This information obtained from the internet:
Premjet PLC
Registerd Office: 5 Jupiter House
Calleva Park
Aldermaston
Reading
Berks RG7 8NN
Incorporated 10/08/2006
Above address is a Company Formation outfit named Sane Choice.
Other information I have obtained indicates they have not actually got an Air Transport Licence (Economic) in the system and don't appear to have applied for an AOC.