whywait im probably not the best person to ask about travel systems as i really dont like them much!
It is important for babies to lie flat, so IMO, unless a really quick school run or something its better to get baby out of car seat and lieing flat.
Having pushed loads and loads of buggies, it amazes me how difficult some are to push / use compared to others. And i think its only when you have pushed an easy to push pushchair that you realise how much more difficult others are.
You also need to consider where you will push the buggy. If only ever on pavements / shopping centres, you can get away with much smaller wheels than in the woods / on the beach etc.
I also dont belive there is a pushchair on the market that pushes well AND is small enough in the town AND fits comfortably a 3 year old (even if they are walking they are likely to use a pushchair occasionaly on a big day out or if poorly etc)
I know so many people who get travel systems and get rid of them by the time the baby is 1 year old as they are big and bulky and NOT that easy to push.
If you want small you could look at the bugaboo bee (which works with the maxi cosi car seat). Very small and fine for pavements / shopping centres / busses and tube.
Quinney zapp is also super small, and can be used with maxi cosi car seat, BUT it doesnt lie back and babies only option is to be in car seat until 6/12 and then seat wont recline.
Not sure if the quinney buzz will fit in a polo, (probably will if you remove the quick release wheels, but trust me that will be a pain and get annoying very quickly). It might... thats an ok buggy, pushes ok ish, and you can get an all terraine front wheel, but still does not push off road nearly as well as a mountain buggy. Also a 3 year old wouldnt fit well in the buggy seat.
Personally i want a mountain buggy or nipper 360 as my all terraine buggy (I live in the country and being easy to push off road is really important to me)... these are the easiest to push buggies you can buy IMO, and once you have pushed them wont want to use anything else. Or else you could try the Jane power track or slalom (but they only fit Jane car seats that dont score so well in crash tests,) or even the proper quinney 3 wheeler of road pushchair.
Disadvantage is that these only forward face, and they are big and bulky...
I also want a Maclaren Techno XT (or XLR which is the new one that takes a coccoon so much more snuggly for a new born baby, and you can fit a car seat on too)
I LOVE this buggy. it fits a 3 - 4 year old, and where its lighter, although it doesnt push brilliantly on proper off road country side, but it can be dragged!
(My bro in laws sister asked my advice as they want a SMALL buggy and to only ever buy 1, i recommended this one, they have it, and are very happy, baby now 9/12)... i think with this you are compromising when they are tiny, but much more practicle for most of their lives!
Also dont get an own brand equivalent of techno XT... my cousins had that and although it looked pretty much the same it was so much heavier to push.
I think you need to go to a pushchair shop and see what you like and what suits you... also if possible borrow a 3 - 4 year old and try pushing with them in it.... even see if the straps fit at all, cause so many dont!
So how are we all this morning? I still have extreamly sensitive boobs, and felt nauseous all day yesturday. Felt "strange", but not "ill", and last night me and OH had the conversation about what if i was pg 
. We concluded just wait and see and if i am its meant to be... 
. I think i dont want to be yet though, i want my October baby!! I just dont know what i want, but im certainly not as excited as i thought i might be... i thought i had a good few months of freedon, and have 2 weddings in the next 6 weeks, one of which im a bridesmaid, and if im not drinking it will be VERY obviouse why.
Also rationally i'm sure its still far too early, but then last night i googled and found lots of people who had the same symptoms as me, very very early, like me. (not to self do not google lol)
On a different note i have found taking charge of yuour fertility have a website here its fab and you can do all your charting there. (no worrying about drawing cover line in the right place etc) Its fab, and having plugged all my info in today is my 1st "infertile" day. Showed OH and i think he believes me that now we are safe to not need condoms 
(which neither of us like!)...
Anyway i hope everyone is ok and will catch up soon.
Today is the last proper day of my summer holiday 
Have a staff meeting tomorrow afternoon (just pre-prep and nursery) and a full boring staff meeting all day Friday... Very dull as most stuff is relevant to the main school age children as opposed to the 3 year olds! Then the children come back on Monday!