hello everyone and welcome Whoops and Luaa.
Whoops as far as I can see you still have 2 long runs and then 2 weeks taper till your Half, so why don't aim to just build up over those two long runs to 10 miles (say aim for 9miles this Sunday and 10miles the next?) If you manage to get to 10miles that only leaves an extra 3 to go on the day, which is a ParkRun, and everyone can jog round a Parkrun (yes that's the sort of nonsense I fool myself with out running 
emummy and others on here are far, FAR more experienced than me but the other thing I would add is that make sure you are getting plenty of rest in between your workouts, so that your body can recover.
Luaa I found (and again, there are others on here far more knowledgeable than me) that the best way to improve your speed is to first improve your stamina. You want to be in the position when you are running that you know you can do the distance comfortably, it's just the clock you are running against. So for instance if the distance you want to get "good" at is 5km, I personally would be building my weekly long run up to 10km over a period of time, so that the 5km distance is well within yourself. Also build different sorts of workouts into your weekly programme - a long run, perhaps a hill session, and a shorter, faster run. Your body definitely responds best when you challenge it in different ways.
So much for the theory! My back is better 3 and a bit weeks later, but I've still got a nasty chest infection and have just started on antibiotics. Not sure when I will be running again but i hope its SOON!