Thanks for your question.
I'm afraid that if you are unmarried, have not paid more in rent/expenses than you would otherwise have paid if you were living in private rented accommodation, have not contributed to the initial financing of the purchase of the property and have not paid for and carried out significant works to the property which has materially increased the value of the property (eg. An extension) then you would not be advised to attempt to make a claim against the property.
If you have actually paid for and carried out works of significance then you might be able to claim under the Trusts of Land and Appointment of Trustees Act but this is not easy or cheap and it cannot be simply upkeep and day-to-day repair of the property. The works generally have to be building works which alter the physical structure of the property (eg addition of room etc) which then make the property more marketable and valuable.
Unmarried partners are not recognised the same was as married partners are, regardless of the length time of the relationship. If you were married and then divorced then the length of the marriage would be taken to be the length of the relationship (ie. 16 years) and you would be able to claim a share of the assets but there is no similar provision for unmarried couples I'm afraid.
I'm sorry that this is probably not the answer you wished to here, but unmarried couples are at a big disadvantage here.
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