Unis will accept individuals with a Higher National Diploma onto their degree programmes to 'top up' their diploma to a degree. However, you will need to approach individual unis to ask if they would be willing to accept you onto their honours year (final year) if you already have a degree in the subject. Highly unlikely.
I cannot believe that a uni will not allow individuals to resit a module they have failed. I thought it was standard policy across all unis. It's true that it's up to individual unis if they allow you to resit the year but all unis should allow you to resit a failed module.