Any ideas what can cause a car to (hard to describe)... Giving it some beens makes it feel like your driving down a bumpy lane (even if your not!), the steering seems to be unstable, jumping around a bit its like your fighting to keep it in a straight line.

This isnt just on lanes though but on normal roads aswell, ant ideas where I should start looking??

 

try getting a 4 wheel alignment, u might have a dogey track rod end, whoever does the alignment should be able to tell u exactly whats wrong

 

Does it get worse as you get faster, does it feel twitchy? If so then like K18LLR says. I changed the track rods, had the toe set and mine is sorted..