Out as far as I know Sarah! UK citizens have been ineligible for the green card lottery for some time now (but Irish are not, including those from Northern Ireland) as there are more than the 50,000 set limit for immigrants in the last five years. If you had been eligible, your application should have been received in Kentucky USA by noon on 06 November 2002.

Don't know about getting your money back (you can ask as you are ineligible and they shouldn't have advised you that you were eligible) but the fact that you paid with your credit card might help your cause as you can presumably get a refund from the credit card company.

I've just found these websites:
http://www.ftc.gov/bcp/conline/pubs/alerts/lottery.htm
http://www.ins.usdoj.gov/graphics/howdoi/divlott.htm
http://travel.state.gov/DV2004.html
which might help.