From that link:Not sure if this helps from Citizens Advice
"If you don't have children and your partner is the sole owner, the only way you may be able to claim long-term rights to the property is if you are able to show you have a 'beneficial interest' in it. This is a way of getting a court to formally recognise contributions you have made towards the home. The court could also recognise an understanding you had with your ex-partner when you bought the home that you would have a share in it if it were sold. If you are able to prove you have a beneficial interest in the home, you may be able, for example, to get the right to live in the home, prevent your ex-partner from living there or get a share of the proceeds if the home is sold".
That’s what happened to the two people Mrs Mottie knew. One made a payment to just put an end to the possibility of court action, the other had to sell up to pay what the court ordered. I think they had had their boyfriend/girlfriend living with them for around 4 or 5 years and both hadn’t had their houses that long before their partners moved in. One couple were engaged when they split up.