I don’t think @Sam87 says anywhere that she currently uses an Apple laptop - indeed the only device she’s been considering so far is a recommendation of an Acer.
Shows how easy it is for a thread to be inadvertently hijacked - in this case, into an academic exercise for Mac users. Not much use I suspect for the OP who surely won’t think that converting to Mac from Windows is a sensible option.
Incidentally, the Windows option is certainly achievable in your price range.
Good luck @Sam87.
I was wondering when someone would realise it’s off topic 
If it helps @Sam87 this link Amazon.co.uk : laptop has the following criteria:
Putting aside the arguments about Macs, the general advice seems to be 8GB RAM and an SSD so the filter I set at amazon should get you started.
Helpful response. 
Would it need to be a USB-C based iPad?
In fairness were several questions at the start to try to establish what the OP wanted/needed, questions which went unanswered.
It wasn’t immediately obvious - but I reckon that wouldn’t have mattered.
The Mac debate gathered pace so quickly, is was job done by about post 5. 
To be honest, I use split screen a lot when video calling, so I think I’d struggle without that feature plus I’d like to stick with a windows OS and a minimum of a 13” screen. Plus I often refer to my iPad separately whilst on a call (I use reference books on the kindle app).
I would absolutely consider a refurb - that is the first thing I look for when replacing any tech 
Most of what I do is PowerPoint and word related with some very light excel.
I’m self-employed, so I don’t have an issue using a personal device. I using video call whilst split screening with a couple of documents and/or webpages.
for me, the 11 inch iPad Pro is the perfect size for word processing. the 10.2 and 10.5 inch iPads are probably good sizes for this task too. 9.7 does feel a little cramped, but it gets the job done.
In many ways it pretty much has become that for me. Thanks to apps like blink and screens, on the few instances I do need Mac functionality, I can remote into it. As for pricing, I get significant discounts thanks to friends and family that work at Cupertino, so it’s never been much of an obstacle for me. It costed me a little under £800 for the iPad and the keyboard combined, though I understand most people will be paying £300+ more.
Fair assessment. 6 or 7 years of software support is the norm for Macs too. Given that the transition won’t complete until end 2022, intel should be support through 2029, possibly even 2030 before they drop support.
You’re not wrong, and that might not help OP much right now, but given that their other devices are part of the apple ecosystem, I think it’s a product worth considering, if not now, then in the future, when they may be better able to afford one. So I’m glad someone threw the MacBook Air suggestion out there, because it’s often regarded as one of the best value laptops you can buy.
This significantly widens your options then. I’ll leave it up to other to recommend a manufacturer. I’ve only ever used Dell and Acer, and my experiences haven’t been great with those. But most will sell their own certified refurbished devices, so they will be fairly safe buys, and in some instances the quality control on those devices is more strict too.
I think I would struggle with anything less than 13” (the screen I’m replacing) and I often am using several documents at once.
Sorry, it’s been a busy 20hours! 
As mentioned by others before then concentrate on SSD for hard drive and 8gb ram.
One of these might fit the bill
For what it’s worth, I upgraded an MSI laptop from a dead hard drive to SSD on the repair man’s recommendation. I couldn’t believe the improvement in performance: next-to-instant boot-up and shut-down. Money well spent (oh, and a doubling of RAM to 8GB). 
To expand on this slightly, depending on the video call app, you maybe able to have your call in Picture in Picture mode whilst still having two other apps open in split view, and also a fourth in slide over, so essentially doing three or four things at once. Could add to the viability of using an iPad.
Older non-pro models may stutter a bit with doing so much though, especially if you throw in an external display. It pushes these devices to their limits.
I haven’t had the time to go through all replies, but for this same reason I’ve always bought/use Lenovo (IBM)Thinkpads for years. From the X220 now to the X270. Buy it used/refurbished and you’ll laugh at all others.
I am not deliberately spilling stuff but it has taken a lot of coffee and teas.
And me. (I’ve had some fun with their K3 Note phone. A dual-sim 6-incher for £103 ! 
).
Can’t go wrong with those.
I’ll upgrade yearly for an avarge 75/100£ after selling my current one.
