Hi Lauren,
Yes, there is a difference between Certificate and Diploma. The Professional Certificate is equivalent to a national Qualifications and Credit Framework Level 3 qualification. The Professional Diploma is at a higher level and is considered equivalent to a QCF Level 5/6 qualification.
The IHE Professional Diploma can be used as the basis for a Personalised Report or a Further Learning report so can help you achieve the required academic base for IEng Professional Registration with the Engineering Council.
Thanks,
Cheryl.