Standard shocks are around £10 a corner but a lot of us prefer something a bit stiffer, try Monroe at around £25 a corner (though the back ones have a reputation for the eyelet opening up) or Decarbon, or ProComp both at around £33 each.
If you don't want a lift you can leave the springs alone, unless it leans or sags.
Bushes, TBH unless you think they are failing it's not worth the trouble of swapping them for standard and polybushes are a matter of taste, I like them and they have stiffened the ride but on my air sprung LSE they made the steering kickback worse, they can be too much.
Definitely worth doing is the panhard rod, the others I'd do as needed, in pairs obviously.