Swimming is one of the best ex's to do, it works every part of your body, try swimming for 10 mins and see how you feel, that will test if your fit or not.
I would suggest cycling in Yorkshire is an excellent way to exercise. I have tried walking up some of them hills, and if you can do it on a bike, fair play to ya.
theres a sticking point. in my childhood, i had to dismount and walk a few times on some of the hills!!!!! Anyone who knows Cusworth hill will know what i'm talking about!!! But then going DOWN them makes it worthwhile i've got a week off starting tomorrow, so i shall start riding my bike, weather permitting!
(in other words, the next day that theres no rain will be the day i start work again knowing my luck)