How to change the collation against all the tables and columns within a database

Onlyway is to create alter statement from INFORMATION_SCHEMA.COLUMNS.

SELECT
'ALTER TABLE ' + TABLE_NAME +
' ALTER COLUMN ' + COLUMN_NAME +
' ' + DATA_TYPE +' '+
CASE WHEN CHARACTER_MAXIMUM_LENGTH IS NOT NULL
THEN '('+(CONVERT(VARCHAR,CHARACTER_MAXIMUM_LENGTH)+')' )
ELSE isnull(CONVERT(VARCHAR,CHARACTER_MAXIMUM_LENGTH),' ')
END
+' COLLATE SQL_Latin1_General_CP850_BIN '+
CASE IS_NULLABLE
WHEN 'YES' THEN 'NULL'
WHEN 'No' THEN 'NOT NULL'
END

FROM INFORMATION_SCHEMA.COLUMNS
WHERE DATA_TYPE IN ('varchar' ,'char','nvarchar','nchar')