Thanks for your question.
If you are moving in with your partner and she is not going to be named on the title to the property (ie. you will be the registered proprietor of the freehold interest) then you should consider making a cohabitation agreement with your partner, this is a deed signed by both parties which states whether or not each party is to have/accrue an interest in the house. It will also deal with other things such as property bought during the course of the cohabitation, debts, budgeting and payment of outgoings. A local solicitor will be able to do it for you and the firm dealing with the conveyance may have a family department who can assist.
In order for it to stand up in court (should it ever be disputed) you should definitely both take independent legal advice on the document and be completely honest with each other about what you both earn.
You may also consider a declaration of trust in which you specify how the proceeds of sale are to be divide in the event it is sold. This is a signed by both parties as a deed and your conveyancer will likely make you aware of the benefits of it.
Finally, and this is perhaps an obvious point, you should make a Will stating what you would like to happen to your estate upon death. You may consider making a provision to your partner in that Will to show that you did contemplate him and to provide some protection from the possibility of him making a claim under the Inheritance (Family & Dependents) Act. Any person who was immediately before your death maintained (wholly or partly) by you could potentially make a claim against your estate. Making provision in your Will would go a long way to discrediting the validity of such a claim.
The above methods really are worth doing despite the expense (not that they are particularly expensive, cohabitation agreement: £300-700 depending on complexity, Will: £150 approx). A great many people decline to pay the initial expense and then only incur higher legal fees in the future sorting it all out as a result of not having such agreements in place.
It may seem a rather cold and clinical approach to what is doubtless a happy time for you both, but the logic of it is fairly plain, it provides security and could save you (both) money in the future. Hopefully, your partner will acknowledge this and engage amicably with you on the issue.
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