you don't need any of this cutting bullshit

you don't even need to jack the car up

the biggest worry is if you snap one of the bolts that holds the plate in place

put a jack under the beam, don't jack it up
undo the 2 small bolts
undo the big bolt
lower jack
put a big socket between the bush and the bodywork
jack the beam back up again
if this fails to pop the bush out, open the door and sit in the car until the bush moves out
clean the inside of the housing with emery paper
smear grease on the new bush and inside the beam
put bush in place
use jack to jack bush into place
put the bolts back in again
15 minutes a side if you don't snap the bolts