Keep an eye on https://www.hotukdeals.com/tag/laptop
There are frequently new laptops listed in your price range with a decent spec that will easily support what you need it too.
As for iPads etc Apple are about to release a new set of products over the next few months so now probably isn’t the best time to buy one
IMHO the base MacBook (Air) is not a machine that will last many years.
Personally I wouldn’t recommend anyone buy a Mac laptop right now before the AS transition (if they can wait).
Not that they’re bad machines, but I would guess the new laptops will be far more powerful for (hopefully) the same money, probably with better stamina too.
My last two laptops were Dells, both around £400 bought new. I got 5 years from the first, and a smidgen under 7 years out of the second.
I would definitely suggest you get something with more RAM.
This - my current laptop is an Acer Aspire 3 with 8GB - I wouldn’t want it less spec’d than that, given that my previous Dell had 6-8GB RAM 7 years ago.
I’d stick with Apple and get a nice MacBook Pro 16”
As someone who is coding for silicon, the dev machine has a lot of issues. And Rosetta 2 is currently having a few issues.
I’d stick with the current Intel Machines until the Apple-Sillicon line has been tested
What size screen are you looking for ?
And I wouldn’t go less than 8gb ram.
My Mac Mini is older than yours and is also doing fine still (although no longer receiving updates).
That still doesn’t change my mind on the current base Air. It has adequate basic performance now and I don’t think it’ll age well.
Obviously YMMV.
I love that you cut the quote off right before I said “if you can wait”!!!
How is it bad advice? Let’s say the AS Macs are dogs, by waiting you’ve lost nothing. In all likelihood you’ve probably even saved money as you could then pick up an Intel machine on clearance.
Apple have proven themselves masters at architecture transitions. There’s no way I’m replacing my 9 year old Mini right now when the current models in all likelihood will be completely eclipsed.
Also, “many years” of support is meaningless to me. Intel is on the way out, they have every incentive to cut support ASAP.
While I also suggest 8gb ram, I wouldn’t worry if the laptop comes with Windows 10S
Windows 10S can be changed to a normal Windows 10 installation very easily for free
What’s the minimum screen size you think would make an iPad viable as a laptop replacement for MS Office tasks?
I have a 9.7” iPad and I don’t think I could routinely use it even for Word documents, let alone Excel.
It’s so subjective based on individual use.
For me Office is Excel, and I’d want a Windows machine with multiple huge monitors, full keyboard and mouse.
Someone else may be happy with Word on an iPad or even just Outlook on a Galaxy S20.
That sounds like £1K+ of kit. For most people, you’d probably want a set up that expensive to be your primary computer!
£400 max is quite decent for an office use laptop, I think.
Just make sure it runs off an SSD and not a HDD, that’s the main criteria. And I’d go for 8gb ram.
For example: https://www.ebuyer.com/974769-hp-255-g7-ryzen-3-8gb-256gb-ssd-15-6-freedos-laptop-3c228es-abu . Youd have to buy and install windows if you wanted it but otherwise this is really over specced for office use if anything.
Seriously whatever you do dont get one that runs off a HDD, it will be sloooooow
I don’t think @anon28892155 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 @anon28892155.
I was wondering when someone would realise it’s off topic 
If it helps @anon28892155 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. 