Last post for tonight!
Thanks for all the help so far.
I managed to capture the tail end of /var/log/syslog, which is reproduced
here.
Looks like 21:42:02 was the point where the boot/start sequence which was hanging got interrupted by my pressing ALT+CTRL+F2 to start a new session.
Just confirming the install was with a netinst CD of Buster 10.7, specifically tailored for i386.