I had a 5 year ban from the Republic of Ireland because I used a fake job offer letter and fake work permit that the agent gave me to submit.

Now I have a certificate of sponsorship (COS) to work as a health care assistant in the UK, but a friend told me that it will be impossible to get a visa because of the Irish ban. I have not started applying for the visa, but I hope to tell them the truth. What chance do I have?