Yes babies are supposed to lie flat - ideally for 6 months but in practise, that isn't always possible. Last time DS didn't like lying flat at 2 months and screamed. Also there are buggies that do not have a carrycot but are suitable for newborns, as long as they lay flat. Graco Evo XT, Mamas and Papas Sola City and Sola 2 are all suitable from newborns. The Sola City has a memory foam (20) to allow baby to be completey flat. I test drove these last week and had in depth conversations. In my opinion a carrycot is a waste of money (some cost over 100) for only a few outings, IMO.
My friend told me to steer clear of icandy as they are big and bulky. Every person I know bought an expensive (500+) pram/travel system such as Stokke, ICandy, Silver Cross, Bugaboo, Jane, Quinny and only used it (iincluding pushchair) until baby was 6/8 months old and then bought a cheap foldaway buggy because their expensive ones were 'too big and bulky'.
I made the mistake of buying secondhand last time (DH was adamant). Bought a Silver Cross linear Freeway, which admittingly would be hypocritical for me to say I loved, but having a saxo meant it didn't fit the boot well! Then we got a Mothercare Urban Detour which was, again big and bulky, and DS never sat right in it. he kept sliding forwards and to the side then the Britax B Agile which has done us 2 years now. We got it because we thought the aeroplane wouldn't take the Urban Detour.
This time I insisted we test drove the buggies and buy brand new. Reasons: DH bought a flag pole and fancy flashing lights for our new Portico. i said if he can afford non essentials, he can afford a brand new buggy. Also I want a brand new buggy that comes with a warranty, does not have scrapes here and there, or studs missing etc, etc and will last us until DC2 is about 3 years old. In testing this theory, I put DS1 into the buggies in pushchair mode as he is tall for his age to see how long the buggies would last.
So far, the Graco Evo is 2cm too wide to fit flat in the boot but will actually fit sideways and probably give us more useable room for other things. The Sola City is exactly the same width as the Britax B Agile which we currently have and fits our Ford B Max.