MissJ, if you can have further diagnostic testing and you feel that you'd prefer to know and make that choice if needed then it's probably a good idea to go ahead.
Are you the other peron who's at the Whittington, or have you moved out of London already? The reason I ask is that they offer quite a good screening/testing programme, much more I think than a lot of other hospitals, and their experience of diagnostics is likely to be much better as a result - that should hopefully make CVS/amnio safer.
As mentioned last week, my risk came back as 1:120 and therefore high risk, mainly on account of being 39. I'm being booked in to have a CVS test on Thursday, and will probably learn initial results next Monday. I will probably continue the pregnancy, dp and I have discussed it, but I really feel a need to know now - the risk seems much worse when you know what it is however much you try to ratiionalise. In my first pregnancy I was just told, by post, that I was LOW risk (their emphasis) although I was already 37 and I didn't ask more, maybe if I'd been told the numbers I'd still have been scared.
I've started a thread to ask others' experiences of CVS/amnio, Miss Jackson, under the Pregnancy topics, if you'd find it useful to read that. Generally the responses I've had on here, my first antenatal/postnatal thread and on that have been quite helpful and supportive.