Fancy - no good advice to add, but I'm in the exact same boat! My DD is also 6mo, co-sleeping, will only feed to sleep, bottle/formula refuser, dummy refuser, spends THE WHOLE NIGHT latched on and occasionally sucking, and wakes every hour atm. We have the odd run of 2 or 3 nights where she maybe goes 3 hour blocks and I feel human, but they're rare. Plus they probably only happen because even she's too exhausted to stay awake anymore.
You really have my sympathy. It's awful isn't it? I spent most of last week sobbing myself awake each morning. I actually reached the point of being desperate enough to try again with the cot, but she screamed, I was too tired to perservere. There's a lot of good advice upthread, but personally, I'm too tired to do anything in the night than just whack my boob back in her mouth and keep my eyes closed.
I found my salvation has been sticking her on DH in the sling one or two evenings a week so she sleeps there, and I get a good baby-free sleep until about 11 when he sticks her in next to me. Am planning that tonight. I may also have a glass of wine. That thought is going to get me through the next 9 hours til bedtime.
Hope you get some sleep at some point in your life ever.