CHAZOZ

Hey I am looking into the skilled visa. But running into a few initial problems and need some advice.. I am a skilled painter, with no qualifications, just "life experience" so to speak. I am aware I will have to undergo a course or get my skills recognised. However PROBLEM.. My previous employer does not have "official letter headed paper" nor is he still in business nor did he pay me with payslips, was all cash in hand although I was through the books (paid tax etc) So I am wondering if a letter without "official letter headed paper" is acceptable signed from him and if a copy of my national insurance contributions from the time worked with him would be acceptable forms of evidence... HELP?