Diplomas

I’m asking what is a HE diploma? and are they acceptable at universities?

I suspect you mean the Access to HE Diploma (or Access to Higher Education Diploma, to give it its full name). Yes, this qualification is accepted at most universities (although not necessarily for each and every course).
Is there are particular course or university you had in mind?

I was thinking about going into a law course however the HE diploma is in law and business