Success! Voyage 5.7.4 successfully Jailbroken.
I owe a big thanks to knc1, geekmaster, grant2, stupidhaiku - thanks for your prompt help and guides, guys.
I'd like to delve further into the details soon, since there currently aren't many Voyage JBs out there. Unfortunately I need to disappear for the next week or two while I deal with some urgent life admin, but I will return.
In the meantime, I can confirm that my experience was identical to stupidhaiku's Voyage JB, including his description of the (lack of) diags menu, post
22;
'...with me interrupting boot then doing bootm 0xE41000. The boot then seemed to stop with the line "sock_init 1888". Note that I never got the diags menu that you show..'
'...[So] I typed exit login and got the login prompt!'
Thanks again everyone. Catch you soon, have a great week.