Unfortunately cheese isn't part of the plan-it's too high in fat and cals. Some people do add a bit at the start to help, but it's not officially allowed! If you want some, the best thing is to use the food planner on the s&s site and see what the figures are like! Also why do you mean about staying under 65cals??
I do often have one slice of cheese, I buy the packs of already sliced low fat cheese so I can work out the kcals and it essentially got no carbs, 0.3g or something I believe, I just find sometimes if I have one slice mixed in with my cottage pie pack it does add a bit of flavour. Em