Jules, you could try ringing Ribeye up again and asking for Tim Wilks, he owned Ribtec before selling up.
Next is Keiron, he worked for Ribtec.
The one who might know unfortunately is Gary from Spartun Marine unfortunately his business went under, however he is around the Gosport area, so someone might know were he works.
If the boat is post 1998 as you say then it will have had a HIN number on the hull somwhere, had to for CE/RCD. Ribtec were quite good at this, although it might take some finding, but normally the transom.
As for the jet, what make is the engine?