Seeing as the old style lightbulbs are becoming obsolete (and illegal to import or manufacture), I wonder if any of the preserved lines have given thought to stocking up, as I can't imagine Horsted Keynes or any of the other perfectly preserved stations looking right with sickly yellow low energy bulbs in their light fittings...
Not all traditional incandescent lamps are affected.
In particular lamps below a certain voltage are exempt, IIRC the limit is 65 volts. So no problems regarding the manufacture or import of 25 volt and 50 volt lamps used on trains, or indeed 12 volts and 24 volts for buses.
Some preserved lines have however changed to LED lamps for saloon lighting due to the much reduced power consumption.
Most heritage coaches have the lights powered from batteries, these being charged by a dynamo driven by a belt from one axle. Due to the restricted speed and limited daily mileage run, these batteries seldom reach full charge.
Removing half the lamps and use of lamps of lower wattage helps to an extent but produces a depressing gloom.
Use of LED lamps is a vast improvement, A 3 watt lamp gives a similar output to a good quality 25 watt incandescent and A LOT MORE light than an inferior incandescent that is also being under run due to nearly flat batteries.
A heritage coach with every light working and all fitted with LED lamps is a splendid sight and a vast improvement over the traditional "heritage gloom"
The West Somerset Railway use LED lamps in most vehicles, possibly after I suggested this.
As regards the lighting of platforms and other premises, most heritage lines IME already use low energy lamps in any fixtures that see regular use. Electricity is a significant expense, and the savings are significant.
For lights that see little use such as platforms that are only used after dark a few times a year then incandescent lamps are fine. 10 nights a year at 5 hours a night is only 50 hours use a year, the lamps should last 20 years.
I would urge that LED lamps be used whenever possible due to the reduced energy consumption and longer life.
If incandescent lamps are essential then I urge stocking up, whether for heritage railways or other purposes.
Many less popular incandescent lamps are already very hard to find. Even those not banned in the UK may be banned elsewhere and production become unviable for the UK market.
Other types are being de-listed for simple lack of demand.