This is the sort of question that most local librarians love. I know that if you walked into my local branch library and asked it, they'd say that Ian Lavender (Dad's Army, Eastenders) lives just up the road, not far from Delia Smith. The librarian would then phone to county reference library (to get them to look up Ian Lavender's agent) and go on the internet to check the contact details for Norwich City FC.
If the questioner then said that they'd rather attract a younger target group, the librarian would probably suggest contacting our local professional football club (Ipswich Town) to see which players could attend the event. Alternatively, they'd try to think of any well known bands based in the area. (For us, that would probably mean Darkness). Libraries stock 'Who's Who' plus stage directories, so they might well be able to point you in the right direction.
Alternatively, are there any well-known radio DJs in your area? If your local commercial station is big enough, some of their DJs might count as 'celebrities' with the younger generation.
One particular celebrity name which comes to mind, is comedian Jo Brand. (Once again, your library might be able to track down contact details). She's a former psychiatric nurse and listed among the supporters of this year's Mental Health Action Week:
http://www.mentalhealth.org.uk/campaigns/mhaw/ friendship-and-mental-health/celebrity-support ers/
Also, check out some of the links here:
http://uk.answers.yahoo.com/question/index?qid =20070303064056AAkosCW
Chris