OK on connecting the 12" to the EQ6 I assume I just need:-
https://www.bintelshop.com.au/Product.aspx?ID=7627 - 2x 303mm GSO Type tube rings
and a
https://www.bintelshop.com.au/Product.aspx?ID=6922 Orion dovetail mounting plate. This says 13" so not sure if it is 13" long or suitable for up to 13". If it is only 13" long is that long enough for the 12" OTA?
will keep looking