Does anyone have any recommendations for cheapish fibre(or fiber) media
converters and where one could buy a pair? They only have to bridge
100Mbit over about 25 meters between houses along a wall, so perhaps no
ducting (only internal-external multimode?) will be necessary.

If anyone has done something similar please let me know - I'm new to
fibre. I know that ethernet would initially be a lot cheaper, but I'm
concerned about lightning and ground voltage differences. It seems quite
hard to find decent kit (ideally with link-pass-through) which isn't
expensive. The stuff on eBay (Allied-Telesyn) and D-Link ones seem
expensive, a bit "consumerish" and don't have many reviews.

With regards to wifi, 54G Wifi is too slow and unreliable - I've tried
it with a pair of WRT54Gs with DD-WRT - and 11n hardware gets quite bad
reviews.

Thanks.