Proper job Neil, I'll post this now for others...
1) Using a 13mm ring spanner carefully remove the 6-nuts holding the cat-pipes to the down pipes
Make sure to spray the studs with WD40 or similar lubricant as the studs are mild steel and secured to the cat-pipes
2) Using a 13mm ring spanner release the 4-nuts from the connecting-sleeves securing the cat-pipes to the primary silencer
3) Carefully slide each connecting-sleeve forward and onto its respective cat-pipe
4) Carefully remove both cat-pipes with the gaskets and the connecting sleeves
5) Carefully remove the metal gaskets from the cat-pipes: use a thin broad blade or similar so as not to damage the gaskets
6) You'll have noticed that the nuts on the connecting-sleeves were uppermost when you removed them; this is not good engineering practice as if the nut were to unscrew then the likelihood is that you'd loose both the nut and the screw so, when refitting, change the connecting-sleeves over so that the nuts are on the underside (hope this makes senseâ¦)
7) Slide the original nearside connecting-sleeve onto the offside bypass pipe (securing nuts down)
8) Using the original metal gasket without sealant, assemble the offside bypass pipe to the offside down pipe: use stainless steel nuts and bolts where possible and make sure to coat the threads of ALL bolts with Copperslip or similar anti-seize grease
9) Slide the connecting-sleeve on to the offside primary silencer pipe and pinch tighten both nuts and bolts (make sure you've applied Copperslip to the threads)
10) Keep checking the alignment and tighten all 5-nuts and bolts to complete
11) Use exactly the same procedure (7 to 10) and assemble the nearside bypass pipe
12) Double check alignments and tightness of the fastenings
The tools: