Bear in mind any sort of kit like this supplied by the armed forces is supplied by the company that puts in the lowest tender through the MOD procurement system. Think of Snatch Land Rovers etc.
I use my issue Silver Shadows for cycling, and for painting jobs in the house.
For actual running I have spent some decent money and bought some proper running shoes from a proper running shop.
I do know some people who say that Silver Shadows work fine for them. However they aren't fitted by a specialist sports shoe fitter and only come in standard sizes. If you go to a proper sports shoe shop you will get your feet measured by some one who knows what they are doing and who will recommend the right sort of sports / running shoe for what you want to do and for your feet.
If you are trying to get yourself fit by doing some decent running then spend some decent money in a proper sports shop and get some decent shoes, not the very average shoes the forces issue. It's your knees and ankles which are going to have to put up with years of phys - so you dont want to skimp on this if you dont have to.