17mm ring spanner 17mm socket and breaker bar 13mm socket Torch Plusgas 8mm socket and 4mm (?) allen key to remove the undertray
If you want to be really through you could buy the following parts (in stainless if you like) which replace the nuts and bolts that are probably very rusty.
2 x cat gasgets (Rover WCM 10480), 6 x 10mm x 30mm hex bolts 12 x 10mm plain washers 6 x M6 full nuts 6 x M6 x 35mm hex bolts 6 x 6mm plain washers 6 x M6 full nuts 1 x Catalyst hanger bracket (Lotus part A111G6001F)
Back the car onto ramps. Remove the under-tray
Soak the Nuts at each end of the cat and the bolts fixing the exhaust hangers in WD40, or the like. Leave overnight.
Often easier to unbolt the 17mm nuts on the inlet side of the cat as they tend to be less rusted, the cat and siliencer can bet seperated more easily once the exhaust system is off the car.
Put a jack or axel stand under the exhaust so it doesn’t fall on your face.
Remove the three exhaust hanger rubbers – two 13mm AF nuts on each
The exhaust and cat should now be free.
seperate the cat and silencer
If you bought new 10mm bolts you can press out the studs from the ends of the cat using a heavy vice and an old socket.
copper grease everything liberally before putting it back together.