Standard for Passing Dissertation

Hey,

So basically due to various issues I haven't been able to spend the necessary amount of time on my dissertation. It's going to be very rushed and practically unsupervised. Luckily at my university, your dissertation grade doesn't have to be used towards your final grade and with all of my other results I'm guaranteed a 2:1 as long as I at least pass the dissertation. Hence, I'm wondering if anyone knows what a third class dissertation would be like? Of course I'd love to do better, but at this point I'll breathe a sigh of relief with a mark of 40. I'm just panicking that I might not even get that as I'm thinking dissertations may be marked a lot more harshly. Does anyone know roughly what standard is required? Any personal experiences? I'm doing it in English Literature if that helps.

It's not ideal and I know most people would be distraught with a 40, but this is the way it's turned out. Any insight welcome