Neuro (and everyone else!) thanks so much for your messages. Absolutely agree with you on the crap man front. Have had no regrets about not "trying to make it work" with father of this baby but sometimes its very hard to know who to turn to talk about some of this stuff.
I had an amniocentesis, where they draw off some amniotic fluid and test it for chromosamal abnormalities. For Downs Syndrome, the test results come back fairly quickly but for other rarer but potentially much more serious syndromes (edwards, pataus) the results take longer to come through.
The heart defect and bowel blockage are of course potentially very serious and although the scan next Monday may show things a little more clearly its likely we won't get a good idea how serious until after the baby is born.
Having read threads written by purplelostprincess (thanks Bouncing for pointing me in her direction) I realise that I should be somewhat grateful that these problems have been picked up ante-natally. Her baby almost died simply because they didn't pick a serious problem until 3 days after she was born. This was at least she has the best possible chance of being treated appropriately.