Yeah, can't see a problem with it. You go walking around houses at night cleaning your custies windows. I'm sure none of the neighbours will mind

Get one of those head torches and flashing led's on the end of your pole and hit the road mate.
Night vision goggles are also an option, about 2K from the surplus store I think. If you wear a head torch though, don't forget not to smile too often, you'll get mozzies stuck to your teeth. If you can't get a head torch, try and get hold of one of those miners helmets. Paint it with Hi Viz paint so you don't get hit by cars when crossing the road from custy to custy though.
You might want to wear soft trainers so you can keep the noise level down to a minimum. If the cops stop you (I doubt it though) just say you've got too much work on and you need to catch up.
Will you still work if it's raining though? Would your custies be OK with rain?
Anyway, let us know how you get on mate.