I spoke to the custodian and author of that website
Airshipsonline : Airships : R32. The references and footnotes to the text are a bit thin so I suspect some oral history has crept in to the "facts".
I asked him the same question: Has the RAF ever operated a rigid airship?. He did not know the answer either.
I suspect that R32 was flown under HMG/Admiralty orders/flag to try to generate US interest to retrieve some of the enormous cost of building. By all accounts, the RAF was NFI in rigid airships and wanted nothing to do with them.
TSR2 and other prototype aircraft were given mil register serial numbers, but they were not operated by the RAF.