Hi again all, please delete/move if not relevant/important - I didn't know if this was worth including here or making a new thread on or such, but I figured I'd provide my account of how the "DS160 number has already been used" issue proceeded for me. It took around ten days (Only six of which were business days, however) for this issue to be resolved; timeline included below:
18th Oct (Friday) - Issue occurred. usvisa-info.com website reports "DS160 number has already been taken" upon New Applicant form completion. E-mailed support e-mails and called the support desk for assistance.
21st Oct (Monday) - Automated response e-mail stated "Unfortunately, sometimes applicants make an error when entering their DS-160 confirmation number. This usually occurs with the letter "I" and numeral 1 or the letter "O" and numeral 0." and requests a copy of my DS-160 Confirmation Form. Immediately provided the requested information and assured them a typo was not the problem.
24th Oct (Thursday) - Received several e-mails in which I seemed to be CC'd, looked to be the support team communicating the problem to the technical team and requesting they assist me. A final e-mail confirmed that the issue had been escalated.
28th Oct (Monday) - A final e-mail from the support team: "The DS-160 number is now available for you to use. Please continue with your visa application process." Was able to proceed past the previously bugged form on usvisa-info.com using the same DS-160 number I was originally provided.
The telephone support team advised me to fill out an additional DS-160 to attain a different -160 number when I rang them on the 18th. Though this wasn't necessary, I made sure to clarify with them wether or not it would cause issues with follow up paperwork, and was assured it wouldn't. Wether you want to pursue the tech-support avenue or simply acquire a different number and proceed is up to you, but it seems to me that it would have been quicker to have just filled out the DS-160 again if that's what you want to do. (It was a nightmare trying to fill out that form before it timed out, so I didn't feel like doing it again - and I also wanted to do everything by the book so I preferred to pursue technical support)
Hope this provides some clarification and relief for anyone currently sitting through this tech glitch. Good luck!