Hi. My thoughts on this is having another external auditor doesnt add any real value to what Telarc already do (an external auditor). The intent of an internal audit is that you know your business better than anyone so you are in the best position for auditing it knowing what you know about your systems and processes. ie you cant hide anything from yourself.
7901:2014 6.2.4 talks about the competency an auditor should have. e) undertaken an appropriate internal auditing course. But 6.2.4 is a “should” not a “shall” so failing this point should only ever become an OI, not a PA.
That in mind here’s a few things google found for me