Wargaming... why? Why are you making the wrong changes to the Centurions and FV4202 P? Why are you buffing their speed? Stop it... its not too late to fix the actual problems!
The Centurion's have a unique role within the game as second line support tanks that can poke ridgelines, take a shot with their high penetration guns and fall back before their lack of armor becomes an issue. By increasing their speed to 50kph you are removing this role from them and shoehorning them into the "normal" medium role, rather than encouraging players to learn their tanks. Worse still is that even after the buff, anything that can be done in a Centurion will be better done in tanks like the M26 Pershing, M46 Patton KR, Type 61 or M46 Patton. The speed changes are not fixing anything about the tank, it just making them worse versions of tanks that are already better than them anyway.
Stop this change before it happens. Fix the actual problems: The DPM and gun handling of the Centurion tanks. While you are already buffing the DPM of both the Mk. 1 and Mk. 7/1 Centurions in the case of the Mk. 7/1 is is an extremely minor buff in a tier where just about every other 105mm armed medium tank has 2300+ DPM.
The Type 61, the Mk. 7/1's closest analogue has 2440 DPM, and better gun handling than the post "buff" Centurion, for a loss of 10mm of penetration, 2.4kph speed and .04 base accuracy. And yet, even after the supposed buffs, the Type 61 will be better at the role you are trying to shoehorn the Mk. 7/1 into. Similarly, the Leo PT A is faster, has the same pen the same base accuracy and the same or better gun handling than the Mk. 7/1 and only loses out on 4 degrees of gun depression. Even the PT A (which is a terrible tank) will be better at the role you are shoehorning the Mk. 7/1 into.
The Mk. 1 fairs better in the DPM department, but will still be outclassed by tanks like the Pershing, STA-2 or Patton KR. (As a note: Since the Strv 81 is also a Centurion, the same applies to it as well. Doubly so because 12 HP/ton is terrible).
The FV4202 (P) is a perfect poster child for how top speed increases dont help these tanks. Youve already increased it to 40kph before this patch, and its still a terrible tank for its role. Now youre trying to shoehorn it into a role that it isnt supposed to fill. And its going to be terrible at it. And you arent even increasing the DPM, which inturn makes it worse than even the "buffed" Mk. 1 Centurion.
Speed is not, nor has it ever been, the problem of the Centurion tanks. Their problems have always been:
1. Their low DPM for their role.
2. Their terrible gun handling characteristics for their role.
Meaningfully improve those 2 things and the tanks will become better. Dont condemn the Centurions to become the same (yet still worse) as every other medium tank. That would be a terrible fate for such beautiful tanks.
(Also the addition of derp guns to the Type 4 and Type 5 is dumb. But thats a separate issue.).