Welcome Holly! That's my due date too. Where are you? I'm going to Queen Charlotte in London (but hoping for a caesarean a week ahead of the due date).
Travel systems... well, to be honest, I'm not sure they are worth the price. I think they are very handy for about 2 - 3 months. Then, I would opt for a lightway MacLaren variety. So, for some 8 - 12 weeks of use, I can't really justify a £200 - £400 purchase. I do recall liking the car seat that snaps into the pram/pushchair. But, apart from that they are just too big and cumbersome to run around with.
Also, if you do get one, I recommend never taking it in a plane. When dd1 was 3 months we took our M&P Pliko to Chicago, and United bent the frame. It was never the same again, so I never used it again.
Since your question was perhaps more about 3 wheelers than travel systems, I should add that we now have a mac 3 which I bought to go running with. I was good for running, but it's a pain in the malls because the back wheels are too wide for some doorways. If you go with a 3 wheeler I would suggest getting one with a fairly narrow span of the back wheels. The phil and ted one is nice (though a bit pricey), but it has no hand brake which killed it for me.