Hi there. I assume you are flying back to Prestwick with Ryanair?? If so, their return flight leaves BOH at 1535hrs.
I've used this flight before when I sat Stage 2 and then when I went back down to resit Stage 2. I had plenty of time to make my flight back to PIK.
Will be using the same flights when I sit stages 3 & 4 in a couple of weeks.
Theres enough time for you to chill out and have a couple of beers in the (excuse for) a departure lounge at BOH after your Stage 2 prior to your flight too which is a bonus