Removing chimney breasts is notifiable work under Building Regulations
ie a building regs application should have been made. Best policy would
be to enquire with your local Building Control about making a
retrospective building regs application. The local building conrol
surveyor will then visit and advise you
You either need to have steel beam inserted or gallows brackets (not
all Councils allow them)
This type of work will be spotted when you come to sell by the Home
Inspector (home condition reports required from June 2007)so its best
sorted out now