This has probably been addressed many times before

I recently changed all my discs and pads and bled the system.
But after a long drive I have developed a knocking noise over bumps and under braking.
I initially thought maybe a warped disc but I am not getting any wheel wobble and the car drives spot on until I slow down and at the last sort of braking coming to a stop I get this thudding sound and I can sort of feel it from the passenger side but not a wobble more a mechanical thumping noise.
I then removed the front wheels and jacked the car up but I cannot find anything obviously loose or see anything missing.

I think the disc and pad change is a coincidence because I have had this noise for a few months but only intermittently under hard acceleration.

Any pointers before I send it for repair greatly appreciated please