Steering wheel shaking under acceleration

The steering wheel vibrates side to side during light acceleration or certain revs, under full load it will do it slightly and disappear in full stride, Any thoughts? I'm thinking it must be the driveshafts, are the cv joints replaceable on our cars? wheels were balanced and aligned last week so are grand, new tyres, going to check the mounts later but I can't see them affecting the steering wheel that way
 
Hw are the track rods/ends? And yeah id check the driveshafts, may not be the cv's as they normally just knock, buy they may be totally gone
 
I assume they are grand if the garage managed to do the alignment ok. What could happen to the driveshaft if it wasn't the cv joints?