I assume there are no children of the relationship.
In order to establish an interest in the property in these circumstances he would have to have done one of the following:-
1. Paid more in rent/mortgage to you than he would otherwise have paid in private rented accommodation. I assume £200.00 is less than he would have to pay combined in rent and bills were he to rent privately in your area.
2. Contributed to the financing of the original purchase of the property or paid off a significant amount of the mortgage using his own capital.
3. Paid for capital improvements to the property which increases the value of the property.
If he has not done any of the above then he would not be advised that he had a claim against the property. You will be fine.
If he had carried out one of the above then in order to establish his interest he would have to make an application to court under the Trusts of Land and Appointment of Trustees Act. This is very expensive, prohibitively so.
He will not be able to claim on the property in the current circumstances and would not be advised to do so by any solicitor he went to see.
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Edited by Thomas on 1/25/2011 at 8:50 AM EST