Hi Philippa, I've cut back on my weekly running distance quite a bit so I don't do much more than about 45 minutes on any given run nowadays, but about 6 months ago I was training for a half-marathon and had my long runs on Sundays. For runs longer than about 75 minutes I found I needed to carry water, and something like Vitamin-Water (or Gatorade, or some drink with salt and sugar in it) seemed to work a little bit better.
I typically didn't eat before a run, but one day my wife cooked pancakes for breakfast on a long day and the run went much, much better. I ate a full breakfast (3-4 cakes, total carb fest
) but didn't run for two hours after I got done eating, so it wasn't on a full stomach.
Longer runs will deplete your reserves and blood sugar, and I find they don't work well with a fast day (or a low-carb diet, if you're trying that combo), so I'd recommend that if you want to do the long runs then you need to accept some compromises to other things you may be trying to do elsewhere. (It's one of the reasons I shifted my running focus from marathon to half-marathon to 10k and now I'm actually looking at optimizing a 5k training schedule.)
The shorter answer to your question is: pancakes, bread, pasta, PB&J... long runs tend to go hand-in-hand with carbs. Eat well, wait at least an hour (two is better), and then go run. Don't run on a full stomach. Bring water with you for 60-90 minute runs, something with electrolyte/sugar replacement for anything longer than 90 minutes.
Find what works for you, though. This is my experience.