Look at simple single page business agreement and answer simple questions and advise

I have a very basic single page business agreement that after 10 months of running would like someone with experience (preferably a solicitor)to look at and answer some concerns i have about it. The document is double spaced and really short and easy, as was a loose draft but never drawn up professionally. My questions include, does it matter where it was signed, does it matter if it wasnt witnessed, does it matter if the company i signed with isnt a specific company but guaranteed, how water tight is my right to receive commission and my liability cover under the agreement. I may think of other questions later. For a professional with experience im sure this is only 15-20 mins work, i suspect most can be done by email but may require a phone call. My ideal person would be a business solicitor, with international knowledge. I would like if possible this completing this week. Once agreeing i will send a scan of the agreement for you to look at with initial questions.