Looks to me like the second select statement is a cartesian product - there is no join linking the rows in FIR_COUNTRY_CODES with COUNTRIES or FIRS, so you will get a copy of all the rows in FIR_COUNTRY_CODES that match the selection criteria for each combination of rows in COUNTRIES and FIRS.
Try the following where clause:
where c.FIR_IDR= 'FF'
AND c.FIR_NAME= 'FIR'
AND c.WORLD_AREA_CD= 'EXC'
Assuming that the FIR_IDR field is a foreign key to the FIR_ID in the FIR_COUNTRY_CODES table, and that FIR_COUNTRY_CODE_ID refers to the COUNTRY_ID in the COUNTRIES table.