i recently replaced my front shock that was 56 quid (got charged 40 quid for the labour) i only found out it was knackered by havin a spring kit fitted.
That probably about right for labour.
But there so easy to replace couldn't you do them yourself ?
Theres one 16mm(i think) bolt at bottom holding shock absorber to rear axle/torsion bar thing (that runs width of vehicle with the coil springs in it)
Remove this bolt and the nut at top of shocker inside the boot that holds shocker strut top cap on.
Slacken this nut by holding shock absorber strut/damper rod with vice grips (or a like) to stop it turning while freeing it off with a spanner till it comes off ..
Then remove shocker from car and replace with new one
P.s you may need 2 jacks, one to jack car up and another one to assist in realigning the shock absorber bolt holes with axle holes on refitting of new shock absorber strut