Judging by signs along road and at rail station there was a major concert at the MK bowl yesterday, possibly airship was associated with TV coverage or follow up video?
Sightseeing flights by airship over London were not uncommon 7/10 yrs ago, don't know if they were promotional/invitation jobs or available at a fare. Such flights are widely advertised in both helicopters and fixed wing a/c sometimes including classics like the Rapide or Lufthansa Ju52.