Any Ideas how to tell if it is subframe or chassis damage or best left to the experts?
Get your car right up in the air and have a bloody good look at it underneath. If it's had a bang which has gone into the chassis rails you should be able to see ripples and distortion. If you can see the wheel is further back than where it should be it may well be that you've bent the chassis, unless you can see the subframe has visibly moved, or is bent. Again look over the subframe for visible distortion or ripples. Paint that is flaking off is a dead giveaway, or clean metal.
If the panel gap on the wing to door get smaller top to bottom then that will also indicate chassis damage.
Giving it a good dose of looking at you really should be able to see any serious misalignment or bends. It's not like it takes a rocket scientist to spot accident damage - it's hardly a black art.