I followed a recipe for sat and pepper chicken, where I fry for 5 minutes, then let it rest then fry for a further 2 minutes before adding to the pan with the veg and seasoning.  The recipe said I could refrigerate some of the chicken (after the 5 minutes) for tomorrow.  I just wondered how long I need to re-fry it for tomorrow to make it safe, and Is it ok to add straight from the fridge or freezer to the oil  
In your description, you've specified that you are intending to re-fry as the method for reheating the chicken that you've stored overnight in your chiller/freezer. However, the title to your question just mentions reheating, and there's actually another great way to reheat the chicken that works well whether the chicken is frozen or chilled. I would recommend using an oven with the broiler + fan mode or an air-fryer. Essentially, when reheating a fried chicken, you'll want to get back that nice crispy outer skin surface that you achieved when you first fried your chicken. So it is essential that you achieve a good dry surface on your chicken. When you chill or freeze the chicken after frying it, it soaks back up moisture and that is why it loses its crispiness. The combined effect of the broiler and the fan running allows for a very effective drying of the chicken's surface while simultaneously bringing the internal temperature of the chicken up until it is safe to eat again. For this you would also find a thermometer with a probe handy so that you can measure the internal temperature to verify. It works directly on a frozen piece of chicken well, because as you can imagine, a frozen chicken would accumulate ice crystals. These ice crystals will melt into water droplets as the broiler heats the chicken up, and these droplets are quickly vaporized and driven off with the fan running. On a side note, it is due to this reason, that especially for fried foods, or just any foods in general that have a crust or crispy outer layer, microwaving them does not give very good results because they get steamed rather than heated and dried. 