We won't be driving to Royston from Sheffield. We are going to stay on a site near Sheffield at Easter as OH is going to snooker at the Crucible, and then to the Peak District for a few days. I thought we would go to near Royston for a few days in March but the cave isn't open then. It's only 30 odd miles from us.
So we will go to Royston some other time and do Duxford and Cambridge at the same time.
I can definitely recommend Duxford..have spent some great days there. It is somewhere to go for the day as there are several hangars to wander around and if you're lucky they may be flying some of their collection. Last time I went a Spitfire and Messerschmidt were up. They do sometimes fly the Sally B (played Memphis Belle in film), I believe , but never seen it airborne.