I now get the following logs, if this helps find where I am going wrong.
Jul 25 02:27:01 example slapd[18371]: daemon: activity on 1 descriptor
Jul 25 02:27:01 example slapd[18371]: daemon: activity on:
Jul 25 02:27:01 example slapd[18371]:
Jul 25 02:27:01 example slapd[18371]: slap_listener_activate(9):
Jul 25 02:27:01 example slapd[18371]: daemon: epoll: listen=8 active_threads=0 tvp=NULL
Jul 25 02:27:01 example slapd[18371]: daemon: epoll: listen=9 busy
Jul 25 02:27:01 example slapd[18371]: >>> slap_listener(ldap:///)
Jul 25 02:27:01 example slapd[18371]: daemon: listen=9, new connection on 20
Jul 25 02:27:01 example slapd[18371]: daemon: added 20r (active) listener=(nil)
Jul 25 02:27:01 example slapd[18371]: conn=26 fd=20 ACCEPT from IP=127.0.0.1:43399 (IP=0.0.0.0:389)
Jul 25 02:27:01 example slapd[18371]: daemon: activity on 1 descriptor
Jul 25 02:27:01 example slapd[18371]: daemon: activity on:
Jul 25 02:27:01 example slapd[18371]:
Jul 25 02:27:01 example slapd[18371]: daemon: epoll: listen=8 active_threads=0 tvp=NULL
Jul 25 02:27:01 example slapd[18371]: daemon: epoll: listen=9 active_threads=0 tvp=NULL
Jul 25 02:27:01 example slapd[18371]: daemon: activity on 1 descriptor
Jul 25 02:27:01 example slapd[18371]: daemon: activity on:
Jul 25 02:27:01 example slapd[18371]: 20r
Jul 25 02:27:01 example slapd[18371]:
Jul 25 02:27:01 example slapd[18371]: daemon: read active on 20
Jul 25 02:27:01 example slapd[18371]: connection_get(20)
Jul 25 02:27:01 example slapd[18371]: connection_get(20): got connid=26
Jul 25 02:27:01 example slapd[18371]: connection_read(20): checking for input on id=26
Jul 25 02:27:01 example slapd[18371]: conn=26 op=0 do_bind
Jul 25 02:27:01 example slapd[18371]: >>> dnPrettyNormal: <mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk>
Jul 25 02:27:01 example slapd[18371]: <<< dnPrettyNormal: <mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk>, <mail=info@example2.co.uk,ou=users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk>
Jul 25 02:27:01 example slapd[18371]: conn=26 op=0 BIND dn="mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk" method=128
Jul 25 02:27:01 example slapd[18371]: do_bind: version=3 dn="mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk" method=128
Jul 25 02:27:01 example slapd[18371]: ==> bdb_bind: dn: mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk
Jul 25 02:27:01 example slapd[18371]: bdb_dn2entry("mail=info@example2.co.uk,ou=users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk")
Jul 25 02:27:01 example slapd[18371]: => access_allowed: auth access to "mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk" "userPassword" requested
Jul 25 02:27:01 example slapd[18371]: => acl_get: [1] attr userPassword
Jul 25 02:27:01 example slapd[18371]: => slap_access_allowed: result not in cache (userPassword)
Jul 25 02:27:01 example slapd[18371]: => acl_mask: access to entry "mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk", attr "userPassword" requested
Jul 25 02:27:01 example slapd[18371]: => acl_mask: to value by "", (=0)
Jul 25 02:27:01 example slapd[18371]: <= check a_dn_pat: anonymous
Jul 25 02:27:01 example slapd[18371]: <= acl_mask: [1] applying auth(=xd) (stop)
Jul 25 02:27:01 example slapd[18371]: <= acl_mask: [1] mask: auth(=xd)
Jul 25 02:27:01 example slapd[18371]: => slap_access_allowed: auth access granted by auth(=xd)
Jul 25 02:27:01 example slapd[18371]: => access_allowed: auth access granted by auth(=xd)
Jul 25 02:27:01 example slapd[18371]: conn=26 op=0 BIND dn="mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk" mech=SIMPLE ssf=0
Jul 25 02:27:01 example slapd[18371]: do_bind: v3 bind: "mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk" to "mail=info@example2.co.uk,ou=Users,domainName=example2.co.uk,o=domains,dc=example,dc=co,dc=uk"
Jul 25 02:27:01 example slapd[18371]: send_ldap_result: conn=26 op=0 p=3
Jul 25 02:27:01 example slapd[18371]: send_ldap_result: err=0 matched="" text=""
Jul 25 02:27:01 example slapd[18371]: send_ldap_response: msgid=1 tag=97 err=0
Jul 25 02:27:01 example slapd[18371]: conn=26 op=0 RESULT tag=97 err=0 text=
Jul 25 02:27:01 example slapd[18371]: daemon: epoll: listen=8 active_threads=0 tvp=NULL
Jul 25 02:27:01 example slapd[18371]: daemon: epoll: listen=9 active_threads=0 tvp=NULL
Jul 25 02:27:01 example slapd[18371]: daemon: activity on 2 descriptors
Jul 25 02:27:01 example slapd[18371]: daemon: activity on:
Jul 25 02:27:02 example slapd[18371]: 20r
Jul 25 02:27:02 example slapd[18371]:
Jul 25 02:27:02 example slapd[18371]: daemon: read active on 20
Jul 25 02:27:02 example slapd[18371]: daemon: epoll: listen=8 active_threads=0 tvp=NULL
Jul 25 02:27:02 example slapd[18371]: daemon: epoll: listen=9 active_threads=0 tvp=NULL
Jul 25 02:27:02 example slapd[18371]: connection_get(20)
Jul 25 02:27:02 example slapd[18371]: connection_get(20): got connid=26
Jul 25 02:27:02 example slapd[18371]: connection_read(20): checking for input on id=26
Jul 25 02:27:02 example slapd[18371]: ber_get_next on fd 20 failed errno=0 (Success)
Jul 25 02:27:02 example slapd[18371]: connection_read(20): input error=-2 id=26, closing.
Jul 25 02:27:02 example slapd[18371]: connection_closing: readying conn=26 sd=20 for close
Jul 25 02:27:02 example slapd[18371]: connection_close: deferring conn=26 sd=20
Jul 25 02:27:02 example slapd[18371]: conn=26 op=1 do_unbind
Jul 25 02:27:02 example slapd[18371]: conn=26 op=1 UNBIND
Jul 25 02:27:02 example slapd[18371]: connection_resched: attempting closing conn=26 sd=20
Jul 25 02:27:02 example slapd[18371]: connection_close: conn=26 sd=20
Jul 25 02:27:02 example slapd[18371]: daemon: removing 20
Jul 25 02:27:02 example slapd[18371]: conn=26 fd=20 closed
Jul 25 02:27:02 example slapd[18371]: daemon: activity on 1 descriptor
Jul 25 02:27:02 example slapd[18371]: daemon: activity on:
Jul 25 02:27:02 example slapd[18371]:
Jul 25 02:27:02 example slapd[18371]: daemon: epoll: listen=8 active_threads=0 tvp=NULL
Jul 25 02:27:02 example slapd[18371]: daemon: epoll: listen=9 active_threads=0 tvp=NULL