CYC £1I think all Providers ear mark the money to differing extents on your account. it protects them and you to a certain extent. just be thankful your maybe not visiting ionity, polar or Instavolt as dread to think what some of those high powered units ear mark.
Chargepoint (Instavolt) £5
Electric Blue £10
Ecotricity £12 (Contactless enabled Efacec units planned to take £24)
Polar 50kW £15
Polar HPC £30
Once they get wise to the fact that the contactless limit has now been increased, I wouldn't be surprised if they also increased the Pre-auth amounts.
They're the only ones off the top of my head, but I'll update if I can think of others.