Thanks for your question.
If both are named as registered proprietors on the legal title to the property at the Land Registry then she will not be able to deny him access to the property by changing the locks.
If jointly named then each party has a right of access to the property which neither can deny the other. This remains the case until there is a Court Order to the contrary I'm afraid (ie. stating that one should not be permitted to access the property.
Should she change the locks then he can simply download LR official copies showing their joint ownership and attend with a locksmith to change them back. He could also probably sue her for the costs of this.
Sorry it could not be better news.
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