Well that sounds like progress to me!
Just to clarify, here is a log entry from just now:
2007-01-10 20:51:48.076521500 status: local 0/10 remote 0/20
2007-01-10 20:51:48.380561500 starting delivery 1: msg 1115398 to remote post@beebee-design.co.uk
2007-01-10 20:51:48.412256500 status: local 0/10 remote 1/20
2007-01-10 20:51:49.451159500 delivery 1: success: 195.188.53.60_accepted_message./Remote_host_said:_250_OK_id=1H4kPx-000305-V4/
2007-01-10 20:51:49.493104500 status: local 0/10 remote 0/20
2007-01-10 20:51:49.566197500 end msg 1115398
Does this definitely mean that the message has been accepted by my ISPs smtp server?
Yes, that's usually what "accepted message" means
Your ISP's mail server, smtp.blueyonder.co.uk at 195.188.53.60, accepted the message for post@beebee-design.co.uk. If it wasn't delivered, then you'll need to ask them why it wasn't. If you quote 'id=1H4kPx-000305-V4/' to them, that might help them in tracking.
I hope that you sent the mail with a valid return address. That way you are able to receive a bounce message if your message cannot be delivered.
Note that none of this has anything to do with SME server, which is doing just what it should be doing.