Nobody could blame you for that golf steve, you’ve been treated appallingly.
The inconsistency of how different customers with the same issues are treated is just sh!te.
I do think that half the time it's an uncooperative dealer who either can't be bothered to raise the issue with VW UK or make a sh!te job of explaining the issue to VW UK to get their funding support.
I've experienced this first hand with Lookers/Benfield (sh!te) and Pulman (great) on a few occasions.
I still think that someone's paperwork who got this done under warranty is the only way to convince a dealership that it is a common issue, not caused by in use damage.
Even if a stone chip could cause these cracks (and impact damage could be seen), that would still demonstrate that the part is not robust enough to be fit for purpose.
If VW carry on treating customers so shabbily, they'll lose customers wholesale. There should be a quicker and easier way to escalate an issue like this.