There’s no such thing as a solid Audit to IBD path, it’s a high-risk, long term chinese whisper.
If you believe you aren’t a desirable candidate because of your interview techniques etc, then ask yourself how can you improve those? If you’re at a target then your grades shouldn’t matter too much aslong as you have a minimum 300-320 ucas points under the old system.
Few Qs,
How is your CV looking? How do you perform on tests?
Why not consider doing a masters and reapply for internships earlier and more prepared next cycle?
Why not consider another division at Banks where interview success rate is far higher?