No idea, I never drove it like that. When I initially complained to the Vauxhall dealer they contacted Vauxhall UK who suggested fitting springs/dampers from one of the German models - this did improve things solo but not towing - I've no idea what the difference was between UK and German models of the Astra but mine was a saloon version, exceedingly rare in the UK.
Getting slightly off the thread, we bought a Vauxhall Cavalier Coupe, ex Vauxhall owned, it turned out to be a Hybrids model for the Swedish Market, different everything, mirrors, camshaft, valves, heater matrix, only found out as my uncle was in the experimental section and checked up on the serial numbers for me.
So everything can be different according to areas.