Hi there!
I also did my undergraduate in Physical Geography at Exeter and completely understand what you are going through. As I am not an academic or university staff I cannot give you a definite answer on what to do, however as a person who got inconclusive results for my diss I can tell you what I did which is thoroughly explain everything in your methodology and discussion.
The information I was given from my diss advisor is that it does not essetially matter if you do or do not get the results you wanted, the most important thing is to explain your methodology, limitations, suggestions for further research etc. In a way need to be able to "support" your inconclusive results, why you got them, support it with existing literature etc.
I would highly suggest reaching our to your advisor or personal tutor and discussing the matter with him. I am sure that they will be able to help you on how to adjust your methodology with a time limit and help you with your worries. You can also see if you are eligible for mitigation which would allow you more time to adjust the project.
It is normal to hit a road bump when writing a dissertation, the most important thing is to not lose motivation, find a way to work around it and explore other methods! As I am sure you know the geography department at Exeter has wonderful staff so you can reach out to almost anyone and I am sure they will. be able to offer technical/methodology advice.
Again, this is all my personal advice and experience.
I hope this helps and fingers crossed it all works out!😊
Laura
Exeter University Student Ambassador