Do you even lift, AF bro?

[Strider]

Mainly I want to lose weight anyway, I'm about 15 and a half stone at the minute (dunno what that is in yank measurements). However a couple years ago when I was actually relatively fit and could run further than 2 feet, I used to always just go around the machine weights, not really thinking about sets/reps or even sticking to any kind of routine.

I guess if I lost about 3 stone I'd seriously consider proper lifting. Just wouldn't know where to start.

As far as beginning a lifting program now, your mobility could be a problematic factor for some of the movements - squats and deadlifts in particular. In your case, I'd focus on nutrition first and getting more active. First, figure out your base metabolic rate (i.e. how many calories you need to stay at your current weight at your current activity level). You can use a calculator like this one: http://www.freedieting.com/tools/calorie_calculator.htm

After you get your daily required calories to maintain your current size, take in about 500~700 less than that number. In the beginning there isn't any need to get specific amounts of protein, carbs, and fats. Just eat good, wholesome foods. Coupled with activity such as brisk walking, machine weights, etc. you will begin to lose weight. Reevaluate your calories on the calculator after you've lost a few kg and adjust your calories accordingly. If you're diligent, I guarantee you will lose weight.