Nvidia reuses numbers for workstation cards, so there's multiple vastly different 'RTX 6000' cards:

  Quadro RTX 6000 (Turing / 2080 Ti / 24GB @ 672.0 GB/s)
  RTX A6000 (Ampere / 3090 / 48GB @ 768.0 GB/s)
  RTX 6000 Ada (4090 / 48GB @ 960.0 GB/s)
  RTX PRO 6000 Blackwell (5090 / 96GB @ 1.79 TB/s)

For £4000 you were likely looking at RTX 6000 Ada listing.