Hi Pips
Have found this site very helpfuly for tracing Cornish relatives & it's free.
http://west-penwith.org.uk/index.htm
In "Search for Resouces" in top right corner type in your family name & it will return any census results for that surname. It is still being developed by volunteers but a great starting place.
Otherwise you can't go past this if you don't already have it.
http://freepages.genealogy.rootsweb.....htm#PageTitle
Happy searching
Ruth