House in negative equity owned with ex partner

[MillyMollyMardy]

Hi I am posting this on behalf of a friend but would really appreciate anyone giving some guidance on what they can or should do as at the moment the are simply ignoring the problem.
It looks like they made a very badly judged decision that they are now stuck with.
They bought a house 10 years ago with a partner. She paid 15% of the property price and they took out an interest only mortgage on the remainder. The arrangement was that she would be "kept" and he would pay the bills and mortgage. He wasn't able to have a mortgage by himself as he was newly self employed but they were able to self certificate for a pretty large sum. X years later they split up. She no longer lives there and does not have keys for the property. She does make any payments towards the property or mortgage but is still on the deeds.
There appears to have been no investment to pay off the mortgage simply payments of the interest which he has defaulted on resulting in a County Court Judgement against her.
He says that the house is still in negative equity although this valuation is based on on line valuations rather than an estate agent visiting.
My first thoughts are that she owns part of the house and is not his landlord therefore should have a key.
That she should be getting valuations from estate agents to find out if they are in negative equity.
She needs to talk to the mortgage company herself to check he is paying the interest.
AAArgh

[greenfolder]

It doesn't make much sense. Surely if he has defaulted on the mortgage there would not just be a ccj, they would have taken action to repossess the property? If she means that he has defaulted and ruined her credit record but is still in the house, she can take legal action to force a sale. And she should.

[MillyMollyMardy]

I think she is going by the fact that he is telling her it is worth less than they paid for it and she can't afford to pay anything if they owe money to the mortgage company. The ccj means I would assume she couldn't t get a loan and
He is still living there so obviously no repossession.
She also says she can't afford legal fees.
She is in a low paid job and all her money went on the deposit.
Is she entitled to a key so she can get proper valuations?