I have fitted some second hand AVO coilovers to my MK5 Escort and going over bumps (severe bumps) I get a knocking noise, like the exhaust is banging against the body. It isn't the exhaust as I have checked and the exhaust doesn't move. I have checked that all bolts are tight so is this the nature of coilovers?

 

NO, should be no noise from coilovers, unless knackered should be silent, check it's not hitting the body anywhere under compression.
tabetha