The CGN flights will continue through S2018 on the EMB195 as they do now.
The additional GRQ flights fill the spare slots in the 2 x ATR72 utilisation needed for the Flybe S2018 timetable released last week.
RNS is interesting because Veuling are dropping their RNS-LGW route for next year and you would think that offered the opportunity to increase frequencies on the SEN route. I doubt Stobart would make a third ATR available just to do that though.