Can you have a WHERE clause with a greater than operator on a composite key?
You can use 

SELECT *
FROM `bbcmapimp_pc_raw`
WHERE (`pc_area`,`suffix`) &gt; ('FO', 'BAR')
ORDER BY `pc_area`,`suffix`


Though actually this seems to have a better explain plan

SELECT *
FROM `bbcmapimp_pc_raw`
WHERE `pc_area` &gt;= 'FO' AND (`pc_area` &gt; 'FO' OR `suffix` &gt; 'BAR')
ORDER BY `pc_area`,`suffix`