UKPassats

Have had new arms front and rear and am still having a very noticeable rattle/knock over bumps and b roads, more notable at low speeds. I'm on AP coilovers but they're not wound down to anything stupid, the garage that did the arms said the knock appears to be coming form the strut, but didn't seem 100% - the rest of the suspension setup has been thoroughly checked by them and/or is new. The car drives spot on, but it's pretty annoying. Are the top mounts susceptible to rattling and how would I go about checking it out?