So sorry to hear that cata.
I can totally understand where both you and your DH are coming from. Did they say which bit of the test gave rise to the risk? I'm wondering if there is any more information you could get through the normal NHS testing (e.g. 20 week scan or quadruple test)? It is good to be prepared, I agree - but I totally see your point too that this is a big chunk of your cushion gone and a 97% chance that it tells you that you don't have to prepare for anything bad at all (and obvoiusly 3% chance it confirms you need to prepare for Downs).
There is no technical/medical rush for Harmony that I know of, so at least you don't have a deadline, you have a bit of time to think about it and maybe do some research on Downs anyway? Probably best to decide once you've processed the initial shock, and then you are less likely to make a decision you regret?
I guess another option could be a private scan to redo the nuchal fold and blood tests if you're still within the right dates? I think that would be a bit less at £180 - don't know if they'd then let you decide a few days later whether to go through with the Harmony or not (so the total is stil capped to 600) but I don't see why not: might be worth calling them and seeing if it's an option if it's something you're interested in? If the risk from the new nuchal and bloods was lower, you might be more relaxed about skipping the Harmony?
Re: the flu jab I had mine last week. No bad side effects that I noticed (had the tail end of a cold anyway, but don't think it got any worse). I have had what I believe was flu once - not an experience I want to repeat! Went to absolutely fine playing a silly board game with friends to collapsing into bed completely out of it hallucinating the room was full of people standing around talking to each other in about 45 minutes flat. Took me AGES to get back on my feet. Can't imagine dealing with that and pregancy, even leaving aside the pregancy risks...
Sorry about your vomiting nevergoogole - glad your GP was able to give you something and sign you off. I do wonder if mine is getting me down partly because I am now busier at work, so not managing to make so many concessions to it. I'm sure rest is a good idea anyway.