Thanks for the replies!
Have been looking into importing out of the UK but spoke to an importer down in Cambridge who seemed to think I'd be better off with a special order on a new one as it'd cost so much to get it here!
The 530D on TradeMe has been there for quite a while - I seriously considered it until I realised 38k is a little high for a 2001 with almost 100,000 on the clock.. For an extra 10k I'd be in the 2006/7 range!
Another option that has been considered (and interested on hearing your thoughts) is the classic manual conversion. Have been doing a bit of reading and everything seems to draw to it being a bad idea... But even if it ended up costing 5k, it'd still be a cheaper option?
As far as I'm aware, they definitely sold the 3-series diesel in manual standard here in NZ (but all NZ-New, nothing ever made it to Japan). The 5-series however, was a special order and therefore a bit rarer.
Cheers,
James