... as now our official line voltage is 400V and that will overload the lamp somehow.

But did the actual voltsge really changed? I strongly doubt...
Because even when the "official" voltage was 3x220/380, the distribution systems were actually set to maintan the range in 220..245V (380..420V across phases), since at least 60's.
The later development (mainly 2000 and later) was targeted to eliminate transmission losses and by that tighten the limits around 230 (or 400)V, so practically exactly where the realmedian was in the "220V" era.

Yes it did change. At least here in Switzerland the voltage tap has been put to the next higher step in 1996. The VHO ballasts I use were from the 80s and still for the old two phase 380V type. And to avoid the stresses on the very rare SLI lamp I used the variac to ramp up the line voltage and supervise the current in a safe manner.
The current voltage in the workshop is now about 405V may not harm the VHO lamp but the SLI bulb.

But did the actual voltsge really changed? I strongly doubt...
Because even when the "official" voltage was 3x220/380, the distribution systems were actually set to maintan the range in 220..245V (380..420V across phases), since at least 60's.
The later development (mainly 2000 and later) was targeted to eliminate transmission losses and by that tighten the limits around 230 (or 400)V, so practically exactly where the realmedian was in the "220V" era.