The whole situation is weird, IMHO.
Despite the place having hosted these Sunday "meets" for 66 years, the Rivvy management continues to regard them as a [Cagiva] Elefant in the Room.
Up to the end of last century, there were motorcyclists based within 30-40 miles of the place who never knew Rivvy existed. A regional TV station once screened a feature about the police going up there with a mobile unit for a road safety exercise; the subsequent description of Rivvy as "a regular meeting place for motorcyclists" resulted in many scratching in the North West of England their helmets in bewilderment, having never heard of the place.
Social media has changed this to an extent, but, as DIC and Beezabryan have pointed out, the Rivvy's own website is seriously uninformative. The local papers may allude to the Sunday meets when some kind of charity event is involved.
There are no special facilities at Rivvy for motorcyclists. (OK, they're only there for one day a week, but it's the highest-attended day.) The bogs are kept spotless, but there's nowhere to hang a skid lid.
The staff are efficient and polite, but somewhat impersonal. Even those bikers who attend Rivvy on a weekly basis can be treated as complete strangers on each visit. (Perhaps that's part of the employees' contract - some kind of "no socialising" rule.)
SK-Art represents the only tangible bike-specific activity at the Barn, but this seems more of a personal initiative than anything the management has laid on.
Here's the SK-Art website:
The Lower Barn, incidentally, is not very well liked by motorcyclists.