Have made considerable progress.
I can log in to a desktop environment, add an ldap user to local groups and define a homedir. The homedir isn't very useful yet (everyone gets the same home directory) but I'm hopeful.
Investigating the issues around dynamic creation of a home directory I see that I might want to use nslcd (which requires libpam-ldapd and libnss-ldapd, instead of libpam-ldap and libnss-ldap - notice the lack of a final d) as it appears to be more flexible - see here: http://arthurdejong.org/nss-pam-ldapd/nslcd.conf.5
I can't seem to make pam_mkhomedir work in conjunction with
nss_override_attribute_value homeDirectory /home/netlink/ (where /home/netlink is a string). Ideally, I'd like to do the override and then have pam_mkhomedir append the netlink id to the string.