Has anyone tried the harder suspension bushes instead as a fix?
Would that massively change the harshness of the ride though?
I haven't... but doubt it would entirely solve the issue. It may reduce the tramping but the semi-cure may be worse than the disease... A road car on hard suspension bushes will not be very pleasant to drive or to ride in. Whilst, in theory, the car on stiffer bushes may handle better, in reality on your average bumpy, potholed road the softer bushed car may well reverse the theory...
Anyway, it would probably be better just to replace the tyres. I've had Conti SportContact 2 and Michelin PS3 on the front of my GTD. I have not had any tramping with either set... wheelspin yes but no tramping...
I've mooted before about the Bridgestone tyres which I have experienced in other fitments not being "death traps" and that it may be something to do with their fitment to the Golf... and this could well be to do with suspension harmonics discussed a few posts back...