2003 Fiat Stilo Rear shock noise

I have recently had my rear gas shocks (and bushes) replaced as I was receiving a large thud as I went over bumps or dips in the road. This is happening on boths sides, offside and near.

Since replacing the shocks, the noise is still there and is getting increasingly worse to the point where I dont like driving the car.

How likely is it to be the axle bushes? If not, what else could it be?

Kind regards