Welcome to Just Answer
I am a Solicitor and will assist you.
I can confirm that the relevant area for law for unmarried couples in relation to property is the Trust of Land Act.
You are able to make a claim under the Trust of Land Act for a declaration as to your interest in the property if you have 1) paid the mortgage, or 2) paid a deposit or 3) added value to the property through renovation.
As you have already stated that you have extended the property and significantly increased the value then you do need to consider making a claim if the amount cannot be agreed between you and also when you should be repaid.
You need to consider family mediation. They can try and help you reach agreement without the need for court. Google family mediation in your area and give them a call to self refer.
If you cannot reach agreement then you can make an application to your local county court on the this form, asking for a declaration as to your interest in the property.
The court fee is £308.
You can also ask the court for an order for sale so that your interest can be realised. When considering an order for sale application the court does need to give consideration to the children residing in the property so the court may decide not to make such an order whilst the children are minors but at least with a declaration of interest you will be able to realise your interest in the property in the future.
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