noise.. mainly when braking..

hi guys

i'm trying to get to the bottom of of a regular knocking from underneath, quite loud when braking, and sometimes heard faintly when travelling at speed

its not the exhaust anywhere, and i barely have to touch the brakes to start the knocking. its not a CV thats 'clicking' round corners

theres a bit of wear in the front bush on passenger front radius arm, but no noise when i move it with a bar myself. there may be a 'bit' of play in swivel bearings but i've not stripped to look yet

is there anything more obvious i should be checking? i really cant imagine what could be giving such a regular/loud knock at this moment, tho i'm sure i'll kick myself when i fin the culprit!!

thanks a lot guys

nev