Jude- Interval training will definitely help your times. I've taken my 1.5mile from 12mins to 8.57!! (at TA TAFS wkend) and most of the improvements have been done in the past couple of months, though I have been gradually building up my training for about 9 months. Gone from strugglin to run for a bus to beating a lot of guys and I'm old too! Sorry, can you tell i'm dead chuffed!
To improve running times you only need 3 running sessions a week.
1: Tempo run- 15-20mins, at a speed where you can only just speak. Start doing 15min sessions, then increase time, then go back down to 15mins but running a little faster. Easiest on treadmill.
2: Interval run- Shuttle between a recovery/gentle jog speed and a FAST run. Jog for 1min, run for 1min. Aim to do this for at least 15mins. As you improve, increase the duration of run/jog times (and, therefore, your overall running time). You can also do this session with shorter sprint bursts, keep these to approx 30secs though.
3: Long slow distance run- go outside and run for at least an hour- don't aim for speed, this session is all about endurance. You should be breathing fairly comfortably.
Hope this helps and inspires! If I can do it...
Feel free to message me for more help.
Oh, last words of wisdom- find a running partner, preferably someone competitive! Good luck