I assume you are in the UK with a RHD m10. My self and others have looked at tubular headers for the m10 but we have yet to find anything that fits. If you have a LHD car then there are loads around 2002 stuff will fit along with some rather beautiful Stahl headers. They do not fit RHD, I have ask the company..
You could always have one custom made but that will cost £400+
Standard cars have a cast manifold then the next piece is the down pipe, then a centre box section then a final rear box section. 4 parts in all.
If your down pipes have cracked make sure you have the proper gear box mounting on it otherwise it will happen again in a couple of months.
you probably can upgrade the rear box + centre box. Rather nice systems can be obtained from
www.larinisystems.com expensive mind! but the usual suspects make them.
You can get a cheap and chearful exhuast from eurocarparts though I had one of their cheap ones that lasted for years!