I'm no expert, but i wouldn't think it is anything more complex than what you first hint at.... a season of BOFRA races would set you up perfectly for Wansfell...

I experienced similar last weekend at Callow... hadn't raced on the fells since late september, and hadn't done anything vaguely similar in distance /climb since the British Champs one-off at Dufton in early Sept... didn't run poorly, but was a way off where i would have liked to be, particularly on the steep climbs... my training mileage has been good and i felt fresh, but didn't have that "race sharpness" for a short, brutal hour of nothing but steep climbs and descents.