If you head North they do flicker a bit and they are very bright when driving South.... joking aside there isn,t a problem with fitting them even in the boot or vanity mirrors. No modifications needed.
http://www.ebay.co.uk/itm/INTERIOR-...del:A2&hash=item20cf2247ea:g:yQcAAOSwFqJWsfXt
Cheers
Dave
Thanks for the quick reply and link I will look into ordering some, what about the polarity issue on the interior bulb?