Thankyou for your responses, in light of all the information we had gathered and the diagnosis from the Dr's we decided we would terminate. But....
Today we had followup with perinatal obs she did another scan and it has shown dramatically reduced hydrops, only fluid at nucchal fold now, cystic hygroma also reduced..... we talked a lot and did more tests but for the moment we have done a backflip on our decision and are waiting for scan at 16wks to see what's happening and test results for any info on the causes. Not all clear by any means but glimmers of hope at the least now.....