I've now heard back from the Rosely House Hotel, and they say it's not them.
They do, though think it might be another nearby house, Ashbrook House (formerly the home of Sir Francis Webster - who he? - and family) but now demolished. The people at Rosely don't know what Ashbrook was used for during/after WWII, but they know that Condor did use it.
Is anyone else familiar with this place?