Southampton City Council's Nuclear Emergency Plan can be found on
http://www.southampton.gov.uk/advice/emergencies/emergency-planning/default.asp
For a quick example of the sort advice give to the public see:
http://www.southampton.gov.uk/images/Sotonsafe%20-%20Part%203%2C%204%2C%205a%20-%20optimized_tcm9-85066.pdf