I am a UK citizen and want to know how best to sue a AZ based company for unpaid consultancy fees of approx $100k.

I was employed as a consultant by company A June09-Nov 11 paid monthly to my UK company bank account plus expenses. The company ran out of money early 2011 but as we were close to a ''deal'' we pressed assuming all back fees would be paid. I had that confirmed in e-mail and verbally and also confirmed in writing by a US based colleague who is in Az but does not want to sue as he is ''scared'' as A has powerful backers. A deal was made - to terms I found strange - which involved the company being merged into another shell company B owned by NASDAQ quoted company C as a wholly owned subsidiary, and which would go to Series A. That process is well underway. Management of A admit my efforts and my contract was valid but offer only derisory stock in A/B and only once the Series A is successful, also stating that they never agreed to pay me back fee and have no money to pay me. I do not want to accept stock and want to sue A. C is aware of the issue but is pressing on with the merger. .