If i way 12 1/2 stone how much protein should i be having a day?

Also is it better or worse for your body if you work out when carrying a heavy cold?

Do not work out if you have a really bad cold. If you have no respiratory distress, you can do light cardio (ie: low intensity) and the muscle movement will help flush lymphatics, and the increased respiration and circulation can help your body metabolize any medications you take for healing and try to get the bug to "hurry out" of your body.

I think protein needs are something like 0.8 to 1 times your body weight in pounds. I don't know how to convert from stone to pounds.