The Fokker 100 (and also the 70) has 5 flap settings: 0, 8, 15, 25 and 42. The former 3 are approved for takeoff.
In my time on that type, about 80% of all takeoffs were Flap 0°. A combination of a short field, heavy TOM and high altitude as usually present on the UK charters from INN usually took Flaps 8° though. This would seem to fit Your observation of the flaps just extending without drooping too much.