Thank you for the replies!
From yesterday evening till now, my daughter went to bed (note: she also has a white noise sheep thats by her cot) at about 19:00 with a bottle last night, woke up around 19:30 and we rocked her back to sleep (took about 15 mins), she woke up again around 22:00 and luckily she fell back to sleep after letting out some wind. She woke up around 02:00 and had milk but even after finishing the bottle she wouldn't go back to sleep till about 04:00 when she fell asleep again. I then left for work around 04:30.
My wife had to get our son ready for nursery so they all woke up at 07:00 the alarm we have set. So from 07:00 till the current time of writing this (19:25) she's had 30 minutes sleep in those roughly 12 hours. Again my wife said she's just had to keep carrying her nearly the entire time. I'm a truck driver so I help out at every point I can but with the nature of the job it's long hours, early starts and late finishes.
To answer a few questions: During the day when she has her feeds she might fall asleep with one of them if we're lucky - and even then if she does fall asleep, like I mentioned before, any slight noise and she wakes up and that's it then, she won't close her eyes again.
As for when we try to get her to take a nap, it's never independent, she is on either myself or my wife when we try, we try rocking her, she has her bottle if she's hungry, we gently bob her up and down a little (this used to be the perfect thing to get our son to nap), we close the curtains in the day and try to keep it dark and quiet, but she just wants to look around and if you try to keep anything from stimulating her she then starts to get upset.
Out on walks she is always looking around and I think she has only slept a handful of times whilst we have been on walks. She goes with my son to our local village hall for a children's event every Monday and my wife has to hold her there as she cries with anybody else.
She does sleep on car journeys but it's only when the car is moving, when you come to a stop she will likely wake up crying and she'll fall asleep again when we start moving again.
I have no worries about her development at all, she seems bright as a button, same with my son - he's 2 years old and can already use the toilet on his own, flush and wash his hands independently. He's crazy about cars and can tell me the make and model of all the hotwheels cars he has, if I show him a picture - for example the Mercedes-Benz logo, he tells me what it is and he'll show me every car on a page that has the same logo amongst cars from other manufacturers. My daughter was already rolling over onto her stomach and looking up and around at 4 months so she's showing signs that she's a quick learner and that she'll be bright and fine in the future - it's just the lack of sleep and naps that's concerning us.
I'm immensely proud of them both and especially my wife for what she does every day when I can't be there, I don't want anyone to think I'm moaning or being dramatic, I know we're luckier than most that they both sleep a decent amount through the night. My daughter is just the complete opposite to how our son was at that age, and like I said my wife and I have no worries about her development but we're just concerned about the sleep in a 24hr period.
Apologies for the long reply and I really appreciate you taking the time to give your tips!