I always check for rust first esp on a Saxo , problem areas I have encountered are boot floor , side inner arches rear lower part , ecu area and check behind weather sills too , do have a look at carpet as now the weather is wet you might find water getting in via sunroof or aerial base , both easy fixes .
As for the mechanical side of things see if it has some service history , recent cam belt water pump change would be a bonus , check if pas works sometimes a problem on my old VTR came down to corroded connections and relay , have a general look around the engine for oil , check condition of oil too making sure it ain't mayo'd up ( head gasket ) probs possibly ! . If you can like I did with mine take it for a short run
