Hi Richard,
I too can confirm not needing proof of marriage in my home country (England), got my JFRV this week 
. Iām not sure if being British made any difference, as i am not sure if whether we can register it there.
We were also told that as long as the marriage/Taiwan marriage license is performed in the court (ie: rather than going to the local 7-11 or your own living room) it is acceptable as legal. Not sure if this part has anything to do with notarizing, etc.
Anyway, once i get my act together i will post some info for other Brits to follow, no guaranteeās it will work but it did for me 
tpetourist