@ianrodger, thanks for that. I think it's time I looked outside just the UK sites.
I have found isolation works well under loudspeakers, especially those that might suffer from a boomy bass. My Tannoys took a step or two towards neutrality when provided with a measure of isolation. They have a lovely full warm mid bass, but previously it could be too much of a good thing with certain recordings.
Ultimately when it comes to isolation I find myself agreeing with geoffkait (shock horror!) in that springs are probably best. However because of practicality and cost these anti vibration pads are a great alternative.
It's also reassuring to see certain speaker manufacturers such as JBL now starting to offer isolating feet and or instead of the ubiquitous spikes.
Furthermore, isolation blocks under monitoring/mixing speakers are also becoming more common in pro use.
