Need a bigger car!

[Yollo]

So I currently have a 2017 diesel Astra. It's been really good over the last 4 years no complaints...but children and prams mean I need more space!

I'm happy with the car and wouldn't change if it wasn't for the space issue but I just need a much bigger boot.

Trouble is I don't have that much money to put into it beyond what my current car is worth

Does anyone have any suggestions on what to look at?

I do 15 to 20k miles per year.

Cars I've initially considered include;

Mazda 6 diesel estate (I read somewhere Mazda diesels are awful?)
BMW 5 series diesel tourer
Skoda Octavia or Superb
Hyundai Tucson or Santa Fe
Nissan X trail or Qashqai

Obviously I'm looking at used motors given the budget but used cars seem really pricey at the minute 🤔

[Yollo]

Thanks for all of the suggestions...including the roof box, it is something I've thought of. I hadn't considered a Zafira. I'm not massively keen on them tbh although most seem to be 7 seaters which could be useful if even more space is needed in future 😂
I do like the Superb and hadn't considered an A6 or an E class but I do like them both and the load space seems huge!
I'd be guessing my current car is probably worth 7.5k to 8.5k and I'm likely to have to get something older but as long as it's solid, spacious and safe that's ok.
Are these older diesels usually reliable?

[Yollo]

Thanks to everyone for their suggestions - I still haven't actually changed cars as I wasn't sure where to head and Christmas kind of got in the way! Anyway I've been able to sort out an increase in budget and I've also thought that looking at an SUV might be the way to go; a solid, reliable and safe car to protect the kids if someone crashes into me is really important and I may be wrong but I think that's more likely from an SUV. Decent kit would be a nice bonus.

So I'm still looking at the Hyundai Santa Fe and Tucson (possibly an IX35 if I spend a bit less) but also a Kia Sportage or Sorento, Honda CRV, Toyota RAV4 or maybe even a Nissan X-trail.

Does anyone have any first hand experience or good knowledge of these cars? Which would most likely be the safest and most solid and reliable? Looking at some CRV models, it looks like it might have 3 isofix child seat points in the rear - can anyone confirm?

[Yollo]

Really useful replies guys, thanks very much. I want to try to get it right with whatever I decide to buy as I intend for it to be something I keep for years.