For goodness sake. All those still saying 'go to a solicitor' - there is no point!
It's awful, but the OP has no rights here. If she had a deed of trust in place then she would have a right to her £2k back plus any increase in equity they had agreed upon in the DOT. She didn't, because he knew full well the implications, and refused to get one. So she has no rights. The law is in place to protect owners of property and unfortunately is very skewed against trusting partners who move in.
The article posted up thread isn't relevant unfortunately. It is talking about the assets being more fairly divided on a break up, but only where they jointly own. It clearly states "The unanimous decision by five supreme court justices makes it clear that even though the home was registered in the names of both the man and the woman, judges are permitted to substitute a fairer division of possessions."
The OP was NOT registered on the house in any way. She has no way to prove that the money she was paying to her 'D'P was going towards the mortgage or home repairs, and even if she could prove it, it still gives her no rights!
The only thing the OP has a right to is any physical items in the house that she purchased on her own bank card as these are legally hers.
It sucks, but that's that.
It's not fair, but it is legally the case, and all the print outs you are encouraging the OP to wave in front of a solicitor will not make a blind bit of difference.
Be nice to this idiot's face and get what you can back off him. I hope he's enough of a gent to give you more than £2k, but I doubt it 
Psychobitch - you would be entitled to nothing I'm afraid as things stand at the moment, have a chat with your other half...