Presumably if you quote the legislation/regulation they will cave immediately?
@NC543210 I would go with a request for a full refund and require them to collect it as it is their responsibility. You can't sned broken glass using the normal postal/delivery services as it's hazardous and obviously you're not going to put yourself at risk by clearing the glass out so it's up to them to figure out how to get it back. Because I am currently procrastinating and avoiding a crap task, I asked Gemini to write an email using UK law and this is what it suggested:
Thank you for your response. Because the item is sold out and a replacement is unavailable, I am exercising my short-term right to reject these faulty goods for a full refund under the Consumer Rights Act 2015.
Please note that because the package contains shattered glass and leaking liquids, it is a hazard and cannot legally or safely be sent via standard postal or drop-off networks due to courier health and safety restrictions.
I am not prepared to risk injury by handling or sorting through broken glass shards to dismantle the calendar. As the retailer, the legal responsibility for arranging the safe return of faulty or hazardous goods rests with you.
The item is safely packaged and available at my address. Please arrange for a specialist courier to collect the package directly from me, and confirm when my full refund will be processed.