If you want to remove a chimney breast on the ground floor that has a chimney breast directly above it on the first floor (and which it therefore supports), you will need to either remove the first floor one (and any chimneys above, up to and including roof level) or provide some sort of support for the first floor chimney. As The Builder states, get a Structural Engineer's advice before you do anything......if you can't find one, then contact the Institute of Structural Engineers (
http://www.istructe.org/) for the names of some in your area. Go to the "Quick Links" section of that webpage (top right) and have a nose around "Find an Engineer"... you'll probably want the Domestic : Lofts/Conversions/Knock Throughs or Structural Inspection/Appraisal sections, just pop in your postcode etc and contact the companies listed for a quote.