I agree with Henry that it sounds very dodgy. With particular note on this statement:
And for that Uk company there is no form 16 and of course my is not taxable
You say "not taxable", but I suspect you have not paid tax because you have not declared your income. An illegal practice, colloquially termed "tax dodging". Unfortunately this raises a number of other questions: Why were you paid cash? Was it because you were employed illegally? Was the company evading tax? Were you (knowingly) evading tax? Did you have the right to work in the UK?
It sounds like you're going to have a hard time explaining this one.