I am looking to build a car with full body and doors so I am looking for a set of drawings for a chassis with low sides, something like the Stylus are there any about?

Failing that I have some ideas myself about the chassis but need to test the strength of my plans, is there anywhere I can get the plans tested without resulting in building the chassis and then have it tested? software?

Software is the 'professional' way, but I've heard it can be difficult to interpret if you aren't experienced.

A balsawood model is a good start. just grab it by the suspension mounting points and give it a good twist, you can easily see where it's weak.

Glue on some plastic card if you plan stressed sheet structures.

A cruciform ladderframe can be quite stiff for a small weight penalty if you use large section tube (50x50, 100x50mm).

This is useful reading:
http://locost7.info/files/chassis/kitcaranalysis_V2.doc
Chapter 5 for ladderframes.