That's sad, to think they still want to re-home her, but ultimately, if Xsar isnt wanted, it may be best for her, poor little girl. Ferne's website looks very well set up, and sponsoring an animal for £25 a year is very reasonable in the circumstances.
Given that you havent had a break in 20 years, and given Minty may not adapt well to sharing her home with another cat, the sponsorship idea might be the more acceptable option. Only you can decide what you want to do ultimately, and I expect that introductions with Minty could be managed, but if Xsar is the cat responsible for the inappropriate toiletting (and I guess there's a fifty/fifty chance it may turn out to be the other cat!) then you would be taking on quite a handful, and you dont know what has triggered the inappropriate toiletting so it could be trickier to fix. (On the other hand, she may not do so if she has a different environment)
I think they would keep her if she behaved - they can't risk their tenancy.
I've asked Ferne for more details - I can't find many cats on the site - they say they have loads, but not alot are on there.
I am still thinking....would it be any harm to give Xsar a chance? If it doesn't work out, then Ferne are there. That said, Ferne replied to me earlier saying they are full and have a long waiting list.
"Thank you for your enquiry. As you can imagine, we do get very full and have a long waiting list. We would need fuller details about the cat in order to consider her for rehoming. Age? Sex? Neutered? Colour? Good with children? Good with other cats/dogs? On receipt of this information I would be happy to put the cat on our waiting list and call you when space becomes available.
I can confirm that the cats usually share living space, unless this becomes too stressful for them. They are fed usually twice daily unless there is a special dietry requirement, and as much time as possible is spent socialising with them, although we rely heavily on volunteers for this when we get very busy. Any medical issues are dealt with swiftly by a local vet, who also visits us regularly to carry out health checks, and all our cats and dogs are brought up to date with their vaccinations and flea/worm treatments.
We endeavour to get them photographed and put onto the website and any potential adopters are home checked before we agree to them going ahead. We try and keep in touch after adoption, and adoption is usually followed up with a volunteer home visitor, if we have any working in the area. We maintain a duty of care towards all animals adopted out, and therefore stress the need for adopters to contact us should they find it difficult to carry on caring for their pets."