Cronshaw is someone I would take the time to listen to!
Yamaha Classic Racing Team under Ferry Brower used Heidenau exclusively for a long time and put many former champions on track on them, not one of these former professionals complained!
But if you are interested talk to Tony Salt, he is the official UK importer, and the only UK supplier, because he is the only one who keeps them at the proper temperature.
With Heidenau there are stories, some people don't like them, complain of bad experiences. Some didn't listen to rim size recommendations from Heidenau, generally wider than for Avons, or tyre pressure recommendations from Tony, generally lower than for Avons. And some of those who complained had been delivered road compound tyres, or badly stored race tyres, or didn't bed them in! They come feeling quite hard but properly run in they are a different beast.