Since this thread has morphed a bit into a "cold weather battery issue" thread I thought I'd add some comments along this line aimed at helping "It's just me";
IJM...you have a particular conundrum; You ride in really cold weather, you have multiple bikes and you want to use a lamp that uses batteries and has a road worthy cut-off beam pattern. Really going to be hard to find something that fits all those requirements. I really do think that a good dyno-setup would be best for someone who really wants to ride in the winter but like you said you have multiple bikes so unless you have a favorite bike for riding in the winter a dynamo set-up isn't going to meet your needs.
That said, using any type of self-contained ( or other ) battery lamp in the winter is likely going to have run-time problems once the temps really begin to fall. Last year I experimented with various set-ups in an attempt to see if I could keep a Li-ion battery warm. It really didn't matter how much insulation I used, eventually the battery got real cold. The fact that you have to mount the battery bag to aluminum tubes doesn't help. The cold just travels down the wire eventually and the pack starts to drop in temperature.
I finally did reach a solution that seemed to work but is a major PITA to go through ( if you wanted to do it on a regular basis ). What I did was set-up a good size battery bag with some light insulation ( cardboard in my case ) and arranged it in a way to work with one of the small-thin butane hand warmers. These butane hand warmers get pretty hot when enclosed so you need to add some insulation to isolate them a bit. When I tested it I used digital thermometers to monitor the temperature of both sides of the battery. Out on my balcony in 10°F weather ( the coldest I get where I live ) the battery maintained a temperature of about 65°F. ( That was with just a a couple mm of thin cardboard/fleece between the heater and the 4-cell flat pack. )
Now if you're going to use a self-contained lamp none of this will help but I thought it worth mentioning in case you have a way to attach an external battery with your Phillips SR. BatterySpace sells a Li-ion battery pack that would work with a Phillips SR but you would have to do some light custom wiring to the lamp to make it work. The battery pack I'm talking about is regulated to 6 volts but only provides 1A output. Not sure if the Phillips draws more than that but thought it worth mentioning.
( **Note about the battery I linked to; I have one of the batteries which I sparingly used with a DiNotte 200L ( AA set-up ). It more than doubled the run time but the battery does self discharge faster than normal ( when not being used ) because of the regulator. )