what you MAY be able to do (and get a solicitor,cos i know jack shit) is give her less than 50% of the house,basicaly she would be entitled to half of everything,any verbal agreement could be classed as only your word against hers,but because you spent xxxx amount on doing up the house,paid all her bills etc you MAY be able to claim that money back from her 50%so she may only be entitled to say 40%
There will be a case against her claim im sure, but i think you should be talking to someone in the know,as i said i know jack shit,
anyhow best of luck matey,remember...... women can be evil at the best of times