Jamie,
Not entirely tongue-in-cheek, you might want to use a bicycle - or motorbike. You can often find interesting view points on airfield boundaries which you miss if you travel by car - or from which you'll get moved on if you park nearby. As a lad a bit younger than you, I spent many happy hours around Midlands airfields (including the V Bomber base at Gaydon and the AW engineering/test flying base at Lutterworth) and saw many interesting and unusual sights. It's also worth trying to get hold of an aviation map of your area (available on line) and you might well spot airfields you don't know about, some of which might be active.
Best wishes
DS