as Tiff say, the boot floor, but pull the trim up in the corners in the boot to see in the inner rear panels,
check the inner front wings by the front struts, I veiwed a couple which had fooked battery trays, not normally a saff weakness but worth a check, also the obvious like panel gaps should be all consistant etc.

When looking for Pauls Cossies we were amazed at how many were advertised as having Full history but actually didnt, so check paper work. and dont rely on proevious HPI checks, get one done yourself, and most important if you are in any doubt or have any niggly worries then walk away,
good luck