"Any ideas on start date/frequency of FR to Beauvais as no flights show when selected???"
It's just a one-off; well, a two-off. Both STN-BVA-STN and LGW-BVA-LGW will occur on only the 14th and 15th September for the rugby. And there will be two flights on both days on STN-BVA-STN and one flight on both days on LGW-BVA-LGW.