Just pulled open the headlights again as I didn't remove all of the old glue from before, and I wasn't very happy with the fit. After scraping out the old glue, it's now sat perfectly and exactly how it was before. Opening them also allowed me to straighten the lenses too.
Tomorrow I'm off to a garage to get the headlights levelled against an MOT testing board, so that they're perfect - shouldn't ever have to touch them then.
Then I'll order the parts to make the relay for the full beam bulbs, and will buy some LED full beams when I'm at it. Should be fun