I think you or your solicitor were foolish to do any work /alterations without a concrete deal on paper ! ........If you were selling your car and a guy comes over to your house and says if you paint it green ,buy new mag wheels,spoiler,tinted windows and fuzzy dice ,he will buy it from you ,without putting it in writing ,would you do it ?? dont see the difference really. Shame on the other party though ! and i sympitise with you . hopefully the work you've done has improved the house,so i would just chalk it up to experience and look to the future ....Good Luck !