Congratulations on the job
Firstly ... does your employer know about your IVA ? You are not barred from directorship from the IVA end of things, but the Company Articles might have a non BR / IVA clause (which could easily be amended).
Authorising payments should present no problems ( in an earlier post I had the authority to authorise payments up to £5 million, when I worked, after that in the NHS, I had to get a counter signatory for a tub of butter! ) Anyway, I was not credit checked for either of these positions.
The credit card, again, as long as it is the company card, in their name, it should present no problems to your IP.
Of course, every situation and employer, are different and do things differently.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014