Is it worth, bearing in mind I have at least 5 stone to loose, focusing on cardio exercise to shift the majority of my weight before I move onto strength training?
The important thing is that you find a kind of exercise which you enjoy - regardless of whether it is cardio or strength.
I think you should consider both cardio and strength training - the benefits of both combined can make a huge difference to how you feel, and can speed up the weight loss journey.
Is it worth, bearing in mind I have at least 5 stone to loose, focusing on cardio exercise to shift the majority of my weight before I move onto strength training?