I think I was in a similar position (maybe slightly worse) back when I did mine. I was getting low - mid 2.1 for my third year modules, and got a low 2.1 on the disso and came out with a 2.1 just about
I would seriously recommend forget trying to figure out the bare minimums and push for a first on every module, then you should at least get a 2.1 on everything (and overall). It was too much of a headache and led to a lot of overanalysing and panic that didn’t help
The dissertation counts for more that the other module individually, and a really higher grade on this can make up for any slack in the others. If you get a first on the disso, and 2.1s on the other modules you’ll likely get a first. Or at least a high 2.1. If they’re grading on a curve, then a high 2.1 could also get round to a first
70% is usually the mark for first, so technically getting 70s on everything will get you a 1st or at least near it