I might be loosing my honours degree over a 10 minute presentation

Clearly if missing it meant you failed the module and hence the degree it was not "pointless" as you say? It was also the largest component of the assessment for the module and therefore the most important part of the assessment simply numerically....
In any event, speak to your personal tutor and/or student union to understand the situation better. Unfortunately as it seems this was not a case of failing due to falling below a grade threshold but due to non-completion or a compulsory element I'm not sure what avenues may be available to you to resolve it unless you gave valid extenuating circumstances and a valid reason why you were not able to apply for these in advance.

Hi there,

Sorry I should have clarified firstly I missed the presentation due to personal reasons (I was deeply struggling with mental health at the time) which I have told my course leader, and secondly by “pointless” I meant it was an extremely easy task that would have been difficult to fail

If you have valid mitigating/extenuating circumstances such as this then you need to get documentation for these (e.g. letters from GP/counselors/therapists etc) and go through whatever your unis extenuating circumstances process is - you may be allowed to progress with the module being condoned, or may be required to retake it (or they may reject it and let the original/current result stand).
It really behooves you to place first the relevant context and circumstances when outlining this situation, as if you try and approach this with the uni in the same circumspect manner as here, without forthrightly stating that you had a mental health crisis at the time or whatever the situation may have been, it's probably going to weaken your case.
I'd strongly recommend you speak with your personal tutor and student union about the extenuating circumstances process and how to approach this - only submitting now that you've received the final outcome of the module is probably not ideal to start with though so you may need to provide some rationale as to why you did not at any point until now apply for extenuating circumstances

That being said, considering that your degree classification is an aggregate of 3 years worth of work, it would be mathematically unlikely for one failed module in first year to bring your overall grade down by a significant amount. Assuming you have done well and passed everything since then, then you can still get your 2:1 and perhaps a 1st at the end of it. If you are worried about this, then again I would ask your personal tutor about what impact this could have on your overall classification.