The 100W old (filament) type are not banned from Sale
- but IMPORT is now banned. That means the limited supplies available will eventually be depleted (except of course sneaky imports will continue for years yet)
NO WAY do the 21W modern type equate to 100W filament. My personal estimate is that the stated rating of the modern type (which is a power consumption rating NOT a light output rating) understates by about 30% ie really you need something like 35W modern to equate to 100W filament in terms of light output.
I have also tried the halogen type with built in transformer - awful. Took it out within a few hours and stuffed it in a drawer. Not bright enough and the colour of the light was poor.
The way forward is surely LED technology. The only issue for that and domestic lighting is now how to get the colour of the light satisfactory for domestic. That IS AVAILABLE for the security lighting type of lamps and they do give very bright light. As my security light bulbs need changing I will be moving to LED type lamps (despite 2.5 times the cost for the lamp) because that will save in the long term.