Do you have sport or S-Line?
You will probably pick up some 2nd hand springs and dampers on ebay or here for next to nothing.
Fitting is £45 hour roughly and book time 3.7 hours, maybe less if the dampers are already fixed to springs, but make sure thats with alignment and preferably hunter alignment.
You might like to think about changing just the springs if you have the S-Line for Eibach Pro springs, lots of discussions about it on here at the moment.
I'm changing mine on my S-Line in the next few weeks, and thats because of the horrible crashy ride you get with the standard S-Line springs.