GRO was only ever Winter only, commencing in late October 2014, to replace BCN, so now than BCN is back 7 times a week for summer season it has replaced GRO. GRO was never on sale for Summer 15.
Reus, on the other hand, was in the Summer 15 timetable originally and was pulled a few months ago. Presumably forward bookings were poor so they added frequencies on other routes instead.
Last weeks Ayrshire Post had a rather large article on how Flybe were considering flights to London City. Officially nothing planned according to a Flybe spokesperson though.