Sorry I've been a bit quiet, I got a bit diverted by Far Cry 2 - lots of driving/boating but enough bangs to keep me happy! (Hey guys, remember to buy fairtrade diamonds!).
Back in the land of SMW, I've been rethinking the game data structure to make it more efficient at culling distant objects during searches. Currently every unit gets checked against every other unit and structure - not so efficient when there's 1000s of them!