Exim relay problem on Woody

[Martin Carwardine & Co <sales@lovecoffee.co.uk>]

Hi,
I've got a Debian server running Woody, and Samba, and clients using 
winXP and winNT,
accessing the Net via squid (ADSL connection).

Everything works fine - including receiving mail (local and internet)
using exim/courier-imap/fetchmail and Mozilla/Outlook clients
configured to use the Maildir on their ${home}.

The problem is sending non-local mail. I've tried different
configurations of exim, but always get: relaying to <x@abc.com.
prohibited by administrator>


Exim was configured to use smart host, which is set as
smtp.btconnect.com as given by BT broadband.

So I have in exim.conf -

smarthost:
 driver = domainlist
 transport = remote_smtp
 route_list = "* smtp.btconnect.com bydns_a"


I have also got -

host_accept_relay = 127.0.0.1 192.168.0.0/24


where 192.168.0.0 is the local network

I also have the following (commented out) -

#local_interfaces = 127.0.0.1


So, any help would be greatly appreciated. Is the problem simply one
of correct exim configuration?