Hi Can any one help with a bit of advice ? I have a fiat punto Dynamic and one of the rear suspension buffers has disintegrated and I wondered whether it is possible to change it without removing the rear spring ?

Nope it's attached to the spring so you need the spring out to unclip it

If one has gone the other is not far behind. The pair cost about £20 from a dealer a few years back. I recall having a jack to raise and lower the axle beam helped a lot as did a second pair of hands.
Welcome to the Forum btw

Rear springs pop out rather easily once the car is supported on axle stands on the sills (bad i know but its only way to securly hold it)

Removing the top gas strut bolts - as the bottoms often seize in, and the rear springs will pretty much then just fall out

my bump stops are playing pin ball inside my rear springs, you can try bonding them back down, but it wont last i suspect

Ziggy