I had to look up what "bonking" meant in the UK because of this thread. Sounds similar to the US/Can word at least for the effects: you hit this point where all of a sudden you just run out of energy and collapse ... but, uh ... I guess the causes are very different.
As for meals I've been really trying to figure that out. I do as many long runs in training in a fasted state as possible to help make sure my body is burning fat for long-distance energy as much as it can. 3-4 hours on an empty stomach is very achievable even if that's on a trail.
It's when you get up to hour 5 ... 7 ... 10 and beyond that I'm now trying to figure out. For the 50 mile in September I didn't pack anything with me and all they had at aid stations was a bunch of high-sugar stuff. Gluten tends to mess with my GI tract while running so I couldn't eat the PB&J sandwiches they had but that shot of fat and protein from the peanut butter might have done a lot of good.
I've been working on becoming and stayng fat adapted over the last few years because I just didn't like trying to choke down those stupid gels, either. Interestingly, one of the things I've learned about myself in doing that is I was also guzzling way, way too much water! I was mistaking a lack of muscle glycogen for hyponatremia. It turns out that, sure, dehydration should be avoided but these days you usually have way more access to water than you need. And drinking too much can be far more dangerous in that situation if you're diluting your electrolytes.
The insidious thing about hyponatremia is one of the symptoms can be increased thirst. That's what I felt. My problem was taking in too much water and my body was so confused due to the electrolyte imbalance that it was prompting me to drink even more. I was probably lucky the last time this happened was in the middle of the North Dakota Badlands and I ran out of water a good 3 miles before the next checkpoint so I was prevented from drinking more than I should. I also promptly dropped out of the race at that checkpoint.
So, word of caution: only drink when you're truly thirsty! Don't follow advice like "drink before you're thirsty" or any advice that suggests you should just mindlessly slam liquids. Too much of anything is too much.