Fantastic work on the running. I'm in a similar boat, was 15st 8lbs when I started running again 8 weeks ago, and have dropped to just under 15st now (target is 13st 3lbs). I have a system that works for me (but obviously might not work for everyone) -
I try to eat 2400 calories a day (my recommended level with moderate exercise), so I just allow myself 12 'portions' of roughly 200 calories, every day. Apart from that rule, I eat what I want (using a bit of googling here and there to get the right data, and forensically examining the nutritional information of everything in the supermarket!).
So - slice of buttered toast, 1 portion, jacket potato with tuna mayo, 3 portions, slice of cake in the office, 1 portion, pint of guinness, 1 portion, can of coke, 1 portion, big bowl of cheesy pasta for dinner 5 portions etc.
It forces me into making slightly healthier choices all the time (i.e. skip the cake and I can have another pint later, but not both like I used to). No quick results, but I'm dropping about a 1lb a week at the moment so something is working. Plus it doesn't feel like I'm on a diet, if I want to splurge 3 portions on a big slice of chocolate cake I can, but I have to make up for it throughout the rest of the day (no bag of crisps on the train, no glass of wine over dinner). Plus, I often 'round-up', so a can of coke with 142 cals I count as 1 portion, which means by the end of the day I'm usually coming in below the 2400 level.
As I say, might not work for everyone, and you have to be very anal about keeping track of everything and not underestimating the amount of calories in things - but after a while it becomes easier to calculate.