Cant help you with any info of the guy who built this model, but like yourself, i am very familiar with the real vessel! Born and raised on Scilly, I have frequently travelled to Penzance on it. Lovely trip on a nice day, but have felt a bit worse for wear after a lumpy crossing!
The local Museum might be able to help you though. The main entrance has a model boat on display, they might have at one point been in contact. The phone number is 01720 422 337 Bit of a long shot but worth a call.
Failing that, might want to try the Steamship Co direct. They may have had some dealings with the chap for advertising etc.
Rgds
Aidi