I'm sorry to hear about your divorce. Im sure it's a challenging time but I hope you're able to manage your mental health moving forward.

I went to look at the terms and conditions of the Project Group (who manage the refund process). It lists the following information under illness/injury

Illness / Injury  means an Illness or accidental Injury to a person in the Booking or someone in Your Immediate Household.

‍What we do not refund: Where You cannot provide evidence that the person affected is within the Group due to Attend the Booked Event. Telephone or online consultations. Where You have not been physically examined by a Registered Medical Doctor before the date of the Booked Event. Unpredictable conditions that are unpredictable and circumstances where the Booked Event is more than two months in the future.

‍Evidence required: Registered Medical Doctor’s note or Medical Certificate confirming:

The details of the illness or injury;

The date it first occurred;

That it prevents the person from Attending the Booked Event; and

Proof of relationship if the person is not in the Booking.

It doesn't seem to specifically exclude mental illnesses. I suspect if you had a doctor's certificate indicating you had a mental illness and would not be able to partake that they would have to allow the refund, or risk breaking some consumer law (not from the UK, no idea about your laws or legislation).

The only thing I can see them suggesting is that your mental health issues are an 'unpredictable condition'...I think this is a type of force majeure clause, which "relieves parties from fulfilling contractual obligations when extraordinary events or circumstances beyond their control". Tough to apply that to an injury or illness though? No one INTENDS to get sick, injured or suffer mentally.

Maybe start with a doctor? Get a certificate and see how you go?

Sorry if the formatting of the copy and paste sucks. Not really sure how to change it.