There are a couple of things to consider here. First issue is that given your partner's age his income would not be considered as being sustainable beyond 70. However if your income can sustain loan repayments the borrowing could be in joint names with the security of the house being offered by him. You will need to ensure that your own position is properly protected by getting the property transferred to joint names. I'm not sure whether CAT exemptions would apply to a Civil Partner. I suspect not, but a solicitor/accountant will clarify.
In that scenario there is no reason as to why a mortgage application should not be successful. However, if your income does not stand up as a repayment source then it's a non runner!