I had this quandary a while ago. Makita battery was the preferred option, ( I have lots of batteries ) but they weren't cheap for what you got, and didn't look value for money, to me at least. Toolstation/Screwfix offerings were considered next, either petrol or battery. Nothing leapt out at me, and reviews are mixed.
So, once more I bit the bullet, and once more, after I had done so, a better option appeared.
I got a Stihl 82 R with the heavy duty gearbox, and it's a beast, cuts through stuff you would think beyond it. I can't fault it, except for the one thing I can't get round- starting a petrol tool at the top of a ladder.
Once I'd bought that, and also lots of AP batteries for my newly acquired battery chainsaw, Stihl decided to bring out a battery equivalent, the 140 R. Thanks Stihl.
Sounds like neither option would suit you, hope you find something that does, good luck.