Bub must be in a rear facing capsule (most decent seats are convertible; can be flipped around) until 6 months or 9kg; once they can hold their head up by themselves you can flip them around. They do take up a bit more room in this position.
Try Safe-n-Sound; My 3 year old is still in his original seat; has removable inserts and adjustable belts.
Was convertible to capsule and also had adjustable incline, as even once you turn them around they still need to be laid back a bit for the first little while. Stay away from shit with built in visors, swivelling bases and all the wanky crap; makes them bulky and annoying (expensive too).
To give you an idea of the range of size; He's 96cm tall now, but he started at 56cms & 3.5kg. He likes his "Racing Harness" too.
The missus used a Phil&Teds 3 wheel pram; folds down flat; wheels come off easily and is light. Easily fitted in the boot of a 323 (not much bigger than you boot). All important if your missus is on the diminutive side and can't lift the pram over the boot lip (cue car damage).
I was surprised how many of the full size prams were more than 12kg; too heavy & awkward for most ladies.
Go to the shop & get your missus to fold down and lift a few dfifferent prams, if she finds it difficult now; it won't get any easier once she's got a little person yelling in her ear.
BTW congrats, they're loads of fun.