firstly-hpi check it-milage and vosa too
google the reg...ask on the forums
check its provenance-it is what it should be...[messed with numbers/engine numbers-check various plastics for date stamps] check drivers side floor number has not been welded in[even the complete floor on that side]
rust-everywhere...under kit,under rubbers
accident damage-check all over

mechanicals-make sure its stone cold listen for piston knock/cams/followers/mains/big ends-these are old abused cars-but very costly to fix
check for transmission noise/synchros/diiff noise etc

good luck