Austin 7’s have a Lucas/CAV 6v generator that on a good day, going flat out will outup about 8 amps, so that’s 8 X 6 = 48 watts minus about 5 watts for the ignition so that leaves 43 watts, not much of a budget when one headlamp could use 32 watts . So no night trials? Some people will fit an alternator but the easiest way to hold back the darkness is using LEDs.
LEDs have a long life if they do not get too hot, most of the cheapies on Ebay fail after a sometimes surprisingly short time they are not engineered thermally or electrically but some good stuff is coming through but they will cost cost you a few more shekels.
The Austin like many cars and motorcycles of the era have BA15d based lamps these are like stop tail lamps without the offset pins.
I am trying some LEDs from BMH Trading in QLD that are sold for motorcycles and are negative earth (yes Austin’s were negative earth until they changed their mind) There are some available for A Model Fords from Logo Lites in the US that I think have the same base that come in positive and negative earth and like these work 6v or 12v that could be worth a try.
As the Chummy was pretty happy just to have lights without all this fancy dipping stuff I have wired them for low beam on the sidelight position and high beam on main so I don’t have to add another switch and these on low beam only draw 3 watts each so they can be used as parkers anyway.