I think Run Wales has summed it up in a nutshell - wait until those niggles have gone completely, maybe do whatever cross-training suits you best and then begin to pick up your running gradually. You need to be flexible in your approach to your mileage, so if you can't do 25 miles in your first weeks then less will do until you feel you can handle more. Then increase your mileage slowly until you can fit in one or two faster sessions, but don't try doing both at once or you'll be back to square one. Remember, running is a lifestyle, eating, resting, stretching and training all go together and help each other along.
Everyone has different tastes, but you could start your day with porridge or cereals, toast and egg or anything that gives you a mix of carbs and protein; wholemeal stuff is best for slow-release carbs. Eat small amounts of good natural stuff throughout the day rather than having large meals, and eat plenty of all different kinds of veg (depending again on what you like) and fruit because they all contain different vitamins and minerals. Protein can come from many sources, but don't overdo the red meat and try more fish (especially the oily ones for the omega heart-healthy fats) and chicken or turkey. I also eat beans and lentils, but not everyone likes them. Carbs can include pasta, rice, potatoes (try not to make them into too many chips!) and again, brown or wholegrain rice and pasta is better for slow release energy. There are lots more things out there for you to try, but I always think that the less processed a food is, the better it is for you! Then give it plenty of time to digest before you run; everyone is different and you will find what works best for you. Hope this helps a bit.
I think you're doing too much too soon and you could very easily end up injured, and that will set your training back; I wouldn't extend the long run at all for the time being if you are training for a half initially, but mix it up and get in some quality speedwork and begin to get in some tempo/race pace sessions as your training progresses. For long runs of 15 miles you don't need anything other than a good varied healthy diet and to pay attention to your hydration; make sure you eat a mix of carbs and lean protein as soon as you return from a hard session. I would stretch properly a few times a week, make your recovery runs very slow and rest a couple of times a week on the days when you feel they will do you the most good. Get the most out of your 'training' days and make recovery just that.
Hi Rosie - it's always good to welcome a new runner! There's always plenty of info in Runners World and the website for new runners so have a look around, but also I would visit a local specialist running shop where you'll be made very welcome; they will advise you on the right gear and shoes to help you avoid injury. Do most of your running at a comfortable pace and if you want to speed it up a bit make sure you are thoroughly warmed up first. You'll find that once your fitness increases, the speed will follow, but the broad base of your running should be reasonably steady. You can also think of joining a club - we're not all speed demons and there will be a group who'll be very pleased to have you with them. Very best of luck!