I feel uncomfortable missing lectures

If you know you're missing out on notes/tips for assessed coursework, then yes, missing those is a pretty poor idea. You have no idea whether you're going in the right direction with your references and at my uni, seminars aren't permitted to directly address coursework topics although they can provide background info.

Try to find someone who was there and ask what you've missed.

If you aren't bothered about the quality of coursework marks, I'm sure you'll be fine.

So I've basically missed the last 5 in one module; 2 because I overslept like an idiot, 2 because I genuinely didn't think they'd be any use and 1 this morning because I didn't think they'd let me in because I was running REALLY late. Aside from that I've only missed 1 or 2 but it's really starting to bother me. Luckily they don't mark attendance but all the same, I feel like crap for doing it. I know it's wasting my money but the only reason I feel this bad is because this morning's is on half of my essay topic. However it's a topic I looked at in my seminar last week and already have a lot of references on. Should I really feel this bad? I'm resolving to attend all of next years especially since that's second year.

What subject do you do out of interest?

I did archaeology.

Even if your seminar was on the precise coursework topic, you won't get great marks for just regurgitating stuff you've heard in a seminar - and referencing a class-based freeform discussion would be a nightmare.