Hi, this is an Irish site, not an English one - and while you may find some pertinent advice here, most of the advice would be within an Irish context.
I do think you do need to find a UK advisor/accountant - one on your local High Street should help. I'm also aware that HMRC have cut back on walk-in clinics but perhaps there maybe one open relatively near to your friend. Tell hiom mt o brign as muc as he can with him to the accountant/advisor/HMRC.
As you've just entered your new tax year, post-April 6th, you should try get this sorted asap.