Have a look here Lex
Themouldmaker.com
http://cart.themouldmaker.com/index.php?p=homeThese are the people I was looking at to possibly produce some Ogres.
They are well recommend and used by a lot of the independent miniature companys
You first need a master mould to turn 1 green into several masters
Mastermould £65 then £2.95 per master cast.
Then the masters are used to make a production mould
Production moulds:
9" : £46.50 each
11" : £54.50 each
Production casting (prices are per kilo):
White metal (60%Pb - 40%Sn) £12.80
Lead free pewter £21.20
You'd get a lot of 10mm figures in those moulds.
While I have plenty of experience at home gravity casting you really need someone with a centrifuge to get the best results especially given how small some of the details are and if it's outsourced to a professional specialist company you know it will get done right.
I just remembered that Eureka will also sculpt and cast miniatures 10mm scale it comes under the 400 club (not listed its special request) so they would need orders for 800 of each figure from 10 different people. This is how the current 10mm stuff was done I think 1 person, can't remember who, paid for most of the stuff to be produced themselves.