Yup can be done as I did this on a mates 205 this weekend ( yes i know i should be doing things to Ezzy but was something i CUD help and do )
We left the manifold on the car os as to avoid possibly having trouble with stripped or sheared bolts... all was done on axle stands so ramps is easily done
Ideally you will need a 14mm spanner bent a bit into an S shape to get to some of the cat bolts and give them a good spray with WD40 or something for a couple of days
I removed the rad to give a little more room and save accidently damaging it, slide the chargecooler to one side,,, no need to totally remove
I split the cat and took off the bottom half first ( whether this is easiest or not is questionable but seemed so for us)
But basically for the downpipe then you need 10mm, 12mm 14mm spanners/socket + the mentioned S shape 14mm or possibly a banana shaped 14mm spanner
Hope some of that makes sense and is of use
we had a couple of the cat shield 10mm bolts shear off
Flexi section (if the same as st165) is just a case of removing the crossmember and then the flexi itself... nice easy job