Well did it. Got lots of advice about what DD deck to get and got very lucky and got a SP10 mk2 from a very nice fellow SNAer. He went out of his way to deliver the deck, rebuild platter/motor and check everything working. Way above the call of duty.
Spent way to much time on Hifi Shark / yahoo.jp and was successfully waitlisted for Yamaha GT 2000 but the cost was ... had to be sensible (still there, Y183,333 and also a YOP PSU available - both shipped for just under $4000AUS) . Also Yamaha + PSU is an end destination. Maybe bare SP10 possibilities are vast for upgrades?
1) Plinth. ?laminated birch / slate or something else. Does anyone have a template for SP10? Any SNAers make these. I know @ENIGMA used to and the plinth for sale recently in classifed was beautiful. The Oswald Tourmaline is also v sexy with recessed/stripped body but USD$5000ish. Do I need to know what arm or length of arm before plinth build?
2) Arm. I think a single arm deck. Sort of tempted by 10" and 12" arms. SME v spendy. Jelco 750's seem to be getting a good wrap. The person I bought the deck off has a 12" Project that he is v impressed with ( also an SME on same deck). Got an Ekos on an LP12 but thought to run 2 decks.
3) Cartridge bit down the line so may come back to you on that.
4) Electrical rebuild. The motor has had some work already but I think the motor/power unit will need to be redone for longevity and insurance. I am aware that fellow forum members have done this. Has anyone experience of Krebs upgrades? http://www.krebsupgrade.com/index.html
Everyone needs a "project" don't they. Now just need a working power amp and speakers - don't ask 
Keith