The Barchester is a hotel which appears in Biggles Takes a Hand. When Anna Lowenhardt came to London, Biggles, knowing the that Ludwig Karkoff and his men would be on the lookout for her, decided that the Barchester was a suitable quiet hotel where she might stay. From this, it can be deduced that the hotel was a small, low profile establishment which was not well-known to foreigners. Not much else is known about the place except that it was close enough to Mount Street for Anna to walk over with her suitcase.
Biggles noted that if Karkoff and his men were to call every hotel in London looking for Anna, they would take a long time to get to the Barchester. A bit strange, it would appear, considering that the letter B comes very early on in a telephone directory.
The Barchester Hotel is again mentioned in Biggles in the Underworld. The master criminal Nicholas Lazor was spotted leaving the hotel at about the time a hotel guest, Lady Crantonby, found that her pearls were missing. This Barchester must certainly be a different hotel from the previous one as it is grand enough for a member of the aristocracy to be staying in it. Perhaps Johns meant to allude to the Dorchester. This is plausible--when Rigby spotted Lazor, he was walking down Park Lane, apparently having just come out of the Barchester. The Dorchester Hotel stands on Park Lane.
Both Barchesters are fictional hotels.