Car appreciation... the aesthetics, the engineering, etc

Pretty much, most rear facing child seats take up masses of room, so if your front seat passenger is taller than 5ft3 you are going to struggle in most "normal" sized cars.
Was one of the reasons we went from our subaru legacy to a 5 series and not a 3

It's definitely tough but our Renault Zoe fit a Cybex baby seat and toddler seat with the front seat still useable and the Tesla fit them both with plenty of room.

I guess it's too late to change car seats?

Also highly dependant on the rake of the seat base that the child seat sits on.

Is this likely to be an issue if I size up to a Golf

Mk6 Golf with a massive swivel base cybex beast in rear facing mode allows for a usable front seat. However it is tighter on leg room that you'd like. Point about seat rake is important.

Worth also saying that when I put no1's forward facing seat in my folks mini there were absolutely no issues or limitations. So it is one of these short term issues while they're short enough to fit rear facing.

Nothing will beat an MPV if you need space in a compact package. Friends of mine have a Mazda 5 and fit 2 adults, two swivel baby seats, a male great Dane and luggage for all in it. I borrowed it and without the second baby seat and the dog the storage space was huge. It's also quite a bit shorter than an Octavia estate.

OT: Congrats!

The Octavia is very roomy, you'll get a bit of extra leg space compared to the other two.

Obviously you can go up to a Superb if you want first class levels of leg room.

The combo of my short legs and the amount of the room in the back of the Superb makes it look like a LWB 7 series when I'm driving and Eazy E is behind me.