Is there actually anyone who isn't poor when it comes to android tablet updates though, I have owned a few from various companies and don't think any of them have ever had more than one major os update.
Well unfortunately that is true. The only way to get guaranteed updates for at least 2 years is by buying a Google/Pixel device.
Sony are good with their updates though. Xperia Z4 tab is still getting updates if i am not mistaken.
I always recommend windows tablets over Android ones for the same reason. There is so much more you can do with a windows tabs and updates will be regular (sometimes TOO regular!).
There are some really good devices near the 300 GBP mark if you are ok to import from a site like Gearbest or Geekbuying. The Cube i7 book for example. Fantastic piece of kit, I am loving every bit of it. The screen is gorgeous, the keyboard reasonably good and best of all, it runs full windows on an Intel Core M3 processor and is fast enough for non gaming tasks.
Can be used as an 11 inch tab as well as a full fledged laptop with the keyboard attached.