I've had one called 'Black Knight', purchased for just over a tenner from a local DIY store called Taskers, and haven't needed to change a lamp in over 2 years. You can adjust the sensitivity and length of activation and obviously set the angle of area covered. Don't know if they are still selling them but worth giving them a ring.
The maximum wattage for outdoor lights cannot go above 250 watts for commercial lighting, 100 watts incandescent and 26 watts compact fluorescent for residential lighting.
I would point out those are US regulations
I'm not sure there is a specific UK regulation, unless you're in a conservation area, national park etc- I can't see anything specific, other than vauge mentions of lux levels.
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