I'm the new owner of The Snail (TOX 79H) - the Morris Minor Pick Up Caravanette with the Fisher Holivan Junior on the back

Full restoration is underway, and I'm trying to find out more about his history. I've done a huge amount of research already, and have written to four previous owners who I had details for from copies of old V5s going back to 2007 (who I'm waiting to hear back from). My V5 says there have been a total of 15 former keepers, so there are 11 more than I'm unable to contact!
I would really like to find out as much as I can about his history and previous ownership, and particularly, in what year the Holivan was put on the back and by whom.
Also, I applied to British Motor Museum Heritage for a certificate, but sadly they replied that 'the post 1964 Morris commercial vehicle factory records were destroyed many decades ago'. So I haven't been able to confirm his original spec or where he was built. Does anyone know how I could find out more?
An MMOC member ('blueangelical') owned The Snail in about 2006 / 7, and was also looking to put together his history file. I've read all her posts, but sadly she was last active in the Forum in 2007.
I would be hugely grateful for any information / help / guidance anyone can give me.
Many thanks!