No, Paddy Maddinson of Bike Radar says 250 lumens, which isn't the same thing as STVZO saying 250 lumens.
As far as I've seen, the regulations are written entirely in terms of lux, so I suspect that he's got his lumens and his lux mixed up.
I've got a front light that's 450 lumens/150 lux STVZO.
Legal requirements are "BS6102/3 or equivalent European standard"*, and noboby's going to get far trying to claim that STVZO isn't equivalent.
The STVZO K-number is different for each model of light, so lazybloke's K1819 is specific to the lights Lidl are/were selling (which may also be available under another name from someone else). There's also a small wiggly line symbol next to the number.
* there's also a rule saying a 4 candela blinky (flashing at 1-4Hz) is OK, but if a light is capable of not flashing, it's got to meet BS6102/3 or equivalent.