Hi, thank you for your question. Just a bit more information required to fully assist you:
-Are/were you married to each other?
-How old is your son?
-Who is now living in the property?
Thank you - she can refuse to agree to this and in those circumstances you would need to apply to court using form N1 and a £355 court fee to execute the deed and for the court to make an order for sale.
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