As far as i am aware you have to have a bumpers for a MOT.
Bumpers are softer at hitting a heads/bodys than the slam pannel, think safety 1st.
OK for shows but not the main road, never know when some one will walk/jump out on you. Let alone the damage to the front of your car or just a bumper.

Think about it. I will go with the boys in blue. thats why all cars are issued with bumpers.
Just mu 2p's worth
Tucker