I've been fitting H4 100/80's to my cars without modification, for the last 10 years. No problems, and brighter lights. And I do know it's actually illegal, but whose going to check. They've never been commented on at MOT time. :-) Mike.
High wattage bulbs can be had from the various car stick on bits type shops - think more along the lines of auto factors / little car bits shops / rally parts places than Halfords. However, you might need to upgrade the wiring to the headlamps, and if you've got plastic headlamp lenses / reflectors they can melt.
The other option is something along the lines of Osram Silver Star or Philips Vision Plus. They're still 55W but produce more light than a standard bulb. Not illegal as they're E marked etc. The Osrams are apparently a bit better than the Philips, but you can get the Philips ones relatively cheaply from Ford dealers parts counters for some reason. Cheaper than ebay, various websites and halfords. I've got the Philips bulbs in my car and they do make a big difference - I previously didn't feel happy doing much above 30 on an unlit road I didn't know with just dip beams, now you can see a lot more, probably enough to do 50ish on the same dark road.
It's fair enough to upgrade the main beams, I've considered it myself, but it's unpleasant to be followed in the dark by someone with brightened dipped lights.
They are correctly set. On dip, the beam cut-off is below headlight level. Only stray light is above that, (I have checked) so I can't see them being a problem when following a car, or indeed, to drivers coming in the opposite direction. I've never been flashed when they've been dipped.
Personally I find HID or Xenon headlights far more dazzling, even on dip, than most halogen headlights. Including mine. :-) Mike.
When you're being followed for some distance on a bumpy or hilly road even correctly set headlights come up at you now and again, and some are noticeably too bright.
£9.99 is cheap for Vision plus, where did you get them from?
Best price I could find was £5.49 each separately or you could buy a pair packaged together for £19.99, I'll let you guess which price I decided to pay.
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