I have just come across the Genealogy.com site and seen your message (posted in 2001!) regarding Sydney Edward Benning.
Sydney was my Great Grandfather and I have been researching the Benning family for just over a year now. The Irish connection is through Elizabeth Lambe, Sydney's wife, who was born in Co. Clare but my father also used to say that we were connected to the Guinness family! Have not found a connection to date - more's the pity!
Please contact me if you would like further information.