My Workout - is it good enough?

Hi everyone, new to this and I plan on tracking what i am doing using My Fitness pal as it's a great app.

On the 4th of Feb, I weighed in at 17 stone 11lbs! i almost died of embarrassment when I saw that and I had to take immediate action.

So I joined the gym and began eating healthier! Since then, I have lost weight, initially rapidly, got down to 15 stone 8 by 21st of March but since then, i have fluctuated between 15st 9lb and 15st 11lb.

Today i was 15st 9lbs, but during that period I have introduced doing weights rather than just running.

What i want to do is steadily lose 1lb a week, with a target of around 14st by end of the year. But i dont know if my work out is sufficient as i only go at lunchtime and i am limited to 30 mins, 35 at a push..

I go between 4 and 5 times a week. in that i do the following:

10 Mins treadmill, jogging and sprinting
20 mins of weight training, 3 sets of 10 reps on several upper body machines, abs and legs too

I tend to do that 3 or 4 times, and then one day a week i will do 20 mins treadmill and 10 minutes on the weight machines.

Once a week I play 5 a side football and once a week i go swimming too.

But am i spending long enough in the gym (i am keeping my calories within the daily limit, apart from the weekends may be) ?

or does anyone have any great workouts that will blast the fat within a short period of time (i.e. 30 mins?)

Any help and advice would be greatly appreciated and good luck to everyone else out there who is working hard to lose weight! I;ve never enjoyed going to the gym as much in my life as i am now, and i used to be seriously active when i was younger!!

thanks again!
Graham