Reddit mentions of Acer R11 Convertible 2-in-1 Chromebook in Blue/Black 11.6" HD Touchscreen Gorilla Glass Intel Quad-Core 1.6Ghz 4GB RAM 32GB SSD Webcam BT Chrome OS (Certified Refurbished)

What is your use case? The cheapest brand new iPad you can purchase right now is the iPad 6th generation for £319... which is already over your budget.

I would almost recommend a Chromebook instead if you want a general purpose machine that can do a little bit of this and that.
For example: Acer Chromebook R11

But if you really wanted the refined iOS experience in a ultra portable form factor like the iPad... Apple does sell refurbished iPad 5th generation for £240

Hey, hope I'm not too late. So, you won't get a backlit keyboard at £250, but you can get the 2-in-1 Acer R11 for about £280.

I've gone through a couple of Chromebooks in the last five years and I just pulled the trigger on an Acer Chromebook R11

They're cheap, small and have great battery life. Since ChromeOS is Linux, drivers and such end up in the mainstream kernel eventually. /r/galliumos is basically xubuntu with everything you need for a flawless experience on supported Chromebooks.