I've put in a LED headlight which came with a reversible heatsink... Didn't have to do anything apart from unscrew a little grub screw, reverse it, screw back on. That was from classicarleds.com - I might've mentioned it earlier in this thread, or another LED one.
I did HAVE to buy the wider rim to get it to fit - bought it from Hitchcocks. The flyscreen does come with the wider rim too. For both, I think you had to have the larger, non-US standard headlight size
This wide rim became standard from a certain year, can't help with exactly when. My 2012 B5 had the narrow rim, hence the upgrade.
I'm trying to find links to all of the above - will post them asap.