Pram for newborn

[Noodles14]

Hi all. Please forgive me for my naivety as I'm a FTM and have no idea about Prams!
So, help me!
The basics...you need a pram for a newborn that lies completely flat yes? How long do they have to be in a flat pram for? Do most prams come with two attachments- a flat one and the tilted one that doubles up as a car seat (if you have an isofix too)?! Please correct me if I'm wrong.
So we are looking for a pram that is not going to break the bank. Certainly don't want to spend anywhere near £1000 so I'm assuming some brands can be ruled out straight away? We walk a lot with the dog so want something fairly lightweight, good on gravel paths and can fit into my BMW 1 series when folded down...does this even exist?!
Any help on brands to look at or advice on what to watch out for is greatly appreciated.

Thanks all for your responses. I am now looking at a pramette (although we are no closer to deciding what we want really!). I just wondered if anybody has the Silver Cross Pursuit or Wayfarer as both look like they come as a pramette option rather than having to add on the carry cot.
Or any other recommendations for a pramette?

Ideally baby would be flat but my babe hated being flat so we then never used the pram. I now wish I'd gotten a travel system where the car seat clicks into the pram. Far handier!

Definitely look second hand. I have recently bought an oyster 2 came with the carry cot and the buggy bit. Was £50 and is in absolute mint condition! Worth a look on gumtree x

Cybex balios S
Mutsy evo
Maxi cosi Adorra
Joie chrome

That was my shortlist for non carrycot options. I didn't look at silver cross though as we're not in the UK and harder to get here. The Mutsy is hard to find in the UK but very nice. That's what we ended up with bit if we hadn't found it second hand, we would have bought the cybex new.

Actually the wheels on both of those Silver Cross prams look small. You'll struggle with surfaces other than pavement with those.

Mamas and papas ocarro is what I went for , seat lies flat so didn't go for the carrycot but got the Footmuff to make sure it's not too exposed for newborn (November baby) and also got the Cybex Aton q car seat to fix on frame as travel system , I love it!