Further to my last post ...
root@debian:/etc# ldapsearch -D "uid=sr,ou=Users,dc=neo,dc=lan" -LLL -W uid=sr homeDirectory
Enter LDAP Password:
ldap_sasl_bind(SIMPLE): Can't contact LDAP server (-1)
...but I've configured this as I would have done, tried both the setup for an Ubuntu client as well as for a Raspbian client.