£200 does not leave much room to work with not for brand new anyway.
i assume you will be doing lots of typing and editing also you will be doing video editing? a lot or little?
i honestly cant comment on video editing large youtube videos on a tablet, maybe something simple is ok but
anything more involved will really become horrible experience i would imagine.
Best thing for you would be a surface pro type device. Where its both a tablet and a full blown computer which can handle some level of video editing and production.
I would really say save up a little more and get a surface pro there are many second had on certain auction site for £400 range. This will give you both a laptop and tablet both in one which i would imagine might offer more flexibility on use. Or there is even the Surface Go 10" which i have seen for £375 for basic model with 64GB HD but this is very small amount. You might want to think about external Hard drive as main storage for video files. If you are taking many videos and pictures 500 will fill up quick let alone 64GB.
if you cant afford that then search for Dell latitude 12 7275 2 in 1 tablet withy keybaord, I have seen the mY3 version if 4GB ram and 128GB hard drive for £300 second had. The battery life is not as good as the surface books but its a good machine.
If you are adamant on laptop only then maybe something along the lines of Lenovo Ideapad 320 around the £240 mark this might be your best bet and can be bought with different configurations but the processor is not the fastest. Whatever you buy dont buy less then 4GB ram ideally 8gb but with your budget that might be difficult.
Something also with the Celeron N3350 CPPU should also be ok in £200 range but this is also not a fast processor by any stretch of the imagination. But good enough for basic internet and video browsing and some basic video editing.
