Option Agreement Challenge Documents

I need a legally sound set of documents that will let me take an option agreement to court or a relevant tribunal and ask for it to be cancelled. The agreement was signed when I was under pressure and before I properly understood what I was accepting, so the core argument is lack of informed consent... (Budget: £250 - £750 GBP, Jobs: Contracts, Legal, Legal Analysis, Legal Consultation, Legal Research, Legal Writing, Litigation, Property Law)