Update on the rear subframe harmonic damper that I had fitted around 10 days ago.
Today my OH and I had a day out in the South Downs, about an hour's drive each way. Part of the drive is on the Surrey stretch of the M25 which is concrete and very noisy. Not so much any more! Normally it is so noisy it makes talking between us a little difficult as the road roar and thumps from the expansion joints is overwhelming. With the damper fitted though it's like being in a different car. The noise is still there but so subdued that we can talk normally and don't have to have the radio on so loud. The only disadvantage is that we can talk to each other.....
Whilst I can't guarantee what others might find but for me, it's made such a big difference, far more than I expected, really pleased with it