As Z-562F states, the classes and the relevant speeds are given in EU-OPS (although they are not solely EU speeds/classes - see EU-OPS, Appendix to OPS 1.430 (c), Aeroplane Categories (b) (2)
The classification is part of the aircraft type's certification and is not something which is varied on a flight by flight basis. The minima found on approach plates e.g. Jepessen are given in terms of aircraft class and so one should know one's aircraft class in order to prepare appropriately for landing, or indeed to prepare properly to commence a flight in the firts place!
Whilst FAA and EU seem to agree on the same aircraft classes / speeds, and that the original aircraft classification does not change on a flight by flight basis. However, FAA certainly says that if circumstances mean that your aircraft is landing significantly faster i.e. at a speed usually applicable to the class above then, for that landing the minimums applicable to the higher class should be be applied. It seems also that EU-OPS states that the minima of the original classification should be adhered to.
Have a look at both the FAA and EU-OPS references given above.
I hope that this helps!