@Hellvelyn
Veterinary nurse and cat enthusiast chiming in here.
Those saying the simple answer is to have her PTS are honestly shocking me so much. She doesn’t add value to your life so she may as well die? Christ. There should absolutely be a list of people who are not suitable to have pets.
Let me tell you that having a pet PTS when it isn’t on medical grounds will haunt you for a long time.
Disturbances can absolutely cause cats to urinate inappropriately, it’s good you had her checked out for medical reasons but seems like that is a dead end.
You said she was better in the chattery. What does the cattery have that you don’t? Perches? Safe space that isn’t frequently disturbed? Pet safe/ non fragranced cleaning products? Smaller enclosure?
Have you considered moving valuable items out of the conservatory and having that as her space? Is this feasible?
The links @Veterinari posted are definitely worth a gander and a cat behaviourist definitely would be worth a look.
www.catvetbehaviourist.com/
Monica is a fantastic Vet who often locums at the London Cat Clinic, she is a wonderful behaviourist that does consultations. She also has an Instagram page you may want to look at.
It’s not just about your needs, it’s about hers too.
Part of signing over a pet to a rehoming centre does include euthanasia if they are not rehomed/ suitable for rehoming. Bare this in mind.