One thing I didn't mention previously is the weight loss I have on a single run. Before I did my 15miler on Sunday I weighed myself and I was 13st 2 (approx 83.5kg). When I got back I was 12st 12 (approx 81.5kg). I've always been like this and I'm guessing it's fluid related but I was wondering if anyone else fluctuated like this? I should add that on the run I generally felt fine, and I considered it a strong and steady run.
On the run, I took a 650ml bottle with me (which I drank all of whilst out). When I got back I downed a pint of lemon and barley and then a pint of water 30mins or so later. I felt thirsty most of the day and drank lots more though the day (mainly water). Again, this is normal for me.
If I am to do anything longer I think I'm going to need something bigger for any longer distances. I can't get on with Camelbaks so I'm going to get a Nathan 2 650-ml bottle holder belt. I know it's extra weight, but I think I'm going to go for it. I currently use a Nathan belt that carries 1 650ml bottle and I get on with it well.
I am a bit conflicted though because I know a lot of people go out for a half marathon and don't need or take any water/fluid. I've never been like that and always feel the need to take on fluid, so I suppose everyone is different. Even as a kid when I used to play basketball I always needed lots of water compared with my team mates.