Some advice needed please

kindeke

My realtionship of nearly 6 years has recently ended, adn I need some advice on how to proceed with the flat we bought together :

We own a 2 bed maisonette, mortgaged joint tenancy ( I think)

Our mortgage is with HSBC, a "Homestart" deal, interest only for the first 3 years, at a fixed rate of 5.55% for the first 2 years.
My partner has moved out, and she can't afford to run the place by herself, but I want to stay there.

At the moment it is still very amically between us, but I am worried that this may soon go out the window when it comes to money, as it so often does...

The situation is as follows :

We both contributed about £5000 to the starting capital, from which we paid the survey, sollicitor and mortgage arrangement fees, and the deposit.
As out mortgage is interest only, no capital has been paid off yet.
We both contributed to the joint account, from where all the bills are paid, but for most of the period we lived there together, my contribution was double or more than hers.
She was going to offset this by doing some work on the house with an inheritance, but we only had the front door replaced so far, at a cost of around £1300.

In total, my contributions to the joint account are roughly double hers.

She said I need to buy her out, but in the current market, the property, even with all the work we've done, may not have gone up in price, give it a while and it may even go down.

If I were to refund her her deposit contribution, and maybe a bit more, and the market keeps falling, I'm afraid that I will be stuck with the rate my fixed rate will change to in February, and because of my personal debt and possible negative equity, I may not be able to remortgage because of that.

Can anyone advise on similar situations, and what my next step should be/ what I am supposed to do?

Botht he mortgage and the house are in both our names, and we are not married.
The house was valued at purchase ( 26/03/07 ) at 112k, and our mortgage is just over 105k


Thanks