Missed a uni re-sit exam due to train cancellations

Sure. I'm going to ignore the unfairness of the situation you've found yourself in and focus entirely on DMU's regulations and procedures. You are fighting a bureaucracy; they don't care about emotion and whether something is fair or not. They only care about their own internal policies, and the cold, hard facts of the case.
You write above that, "I’ve appealed and now have a formal complaint being investigated by Student Casework Services". Has the appeal yet been heard by the Academic Appeal Panel, or is it still pending? Did you raise the formal complaint because the appeal was not upheld? Or did you raise the complaint alongside the appeal?
Charpter 6 of DMU's General Regulations, "Academic Appeals against Assessment Board or Research Degrees Committee decisions" make it clear that you must appeal with 15 days of begin notified of the decision against which you're appealing. When were you notified that you would not be allowed to progress to the next year? Did you appeal that decision within 15 days?
The same regulations state that there only three grounds upon which you can appeal for reconsideration of an Academic Appeals against Assessment Board or Research Degree decision. I'm assuming we can rule our "Prejudice or bias", which leaves us with:
• Procedural irregularities: "There were procedural irregularities in the conduct of examination or assessment procedures of such a nature as to create a reasonable possibility that the result may have been different if it had not occurred."
• Significant mitigating circumstances: "There are circumstances that materially affected a Students performance, for which supporting evidence exists and for which the university did not already have measures in place to prevent/inform consideration of this at the Assessment Board, and it was not reasonably practicable for the Student to inform the university before the Assessment Board made its decision."
Which of these grounds did you use as the basis for the appeal? I assume you would have gone with "significant mitigating circumstances". Is that right? Or did you just outline what happened on the day, and the impact it had, and leave it up the Academic Appeal Panel to determine whether you were targeting "procedural irregularities" (perhaps the 15-minute grace period) or "significant mitigating circumstances" (the travel issues)? Or perhaps you appealed on both grounds?
Has it been 10 working days since you raised the appeal? If so, and the Student Casework Manager has not dismissed the appeal following it's initial consideration, then that's good news. (They can dismiss it as being too late, not meeting one of the eligible grounds for appeal, etc. meaning it wouldn't actually get to the Academic Appeal Panel.) Alternatively, if is was dismissed within this period, has the case yet been referred to the Office of the Independent Adjudicator (OIA) for review?

Thank you for your detailed response. Yes, I did raise my appeal within the required timeframe — within 15 days of receiving the decision. The grounds I relied on were:
The Early Resolution dismissed my case, because they accepted my deferral and said I can sit the exam in November, but said due to the pharmacy regulations, I cannot progress onto the next stage of study without having passed all of the must-pass modules. I contacted the GPhC (the regulating bodies of the programme) and they literally contacted DMU pharmacy to remind them that they can seek approval for trailing a module if it is necessary! I had escalated it formally to Student Casework Services, highlighting proportionality, fairness, safeguarding, and the GPhC’s stated willingness to allow progression exceptions in exceptional cases if the university requests them. My formal complaint has been received by the faculty and I am still awaiting a response.

At this stage, my appeal is still pending, and I am awaiting the outcome.

I have a meeting with the pharmacy admin team on Monday to discuss my position on the programme, not really sure what it’s going to entail or why they’re going to tell me, but they know this has affected me so much, since the 11th August. It is unfair for a student who achieves good grades and is not mischievous to be sitting an entire year out for just ONE exam in November.

I hope this gives you an insight as to what’s going on.

Thanks. Well, it seems to me that you've done everything you can right now to give you the best chance of a successful appeal.
The challenge, I suspect, will be that the university are of the opinion that "due to the pharmacy regulations, I cannot progress onto the next stage of study without having passed all of the must-pass modules". Hopefully, the fact that you've managed to get the GPhC to specifically contact the university and "remind them that they can seek approval for trailing a module" is encouraging. The "default" option will likely be for the university to insist that you can't progress, so half of this battle will be in trying to make then realise that this isn't the "easy" option for them. You've made the option of trailing a module a little easier for them, by having the GPhC contact them. And you've made the "waste a year doing one module" option harder by kicking-up a fuss, appealing, and making a formal complaint to Student Casework Services. All you can do is continue along those same lines: make is easier for the university to accept trailing a module than not.