It would have been a good idea if this loan agreement had been registered against the property as a charge.
You could take your mother to court to get an injunction to prevent her selling the house or you can place a restriction against the property which will prevent it being sold unless the restriction is being removed. The loan agreement is sufficient evidence for the Land Registry to agreed to place the restriction on the property.
It’s a relatively simple job for a solicitor but a bit more complicated if you are an individual as there are about 40 different types of restriction.
A solicitor is likely to charge between £200 and £300 for doing the job.
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