After reading about a lot of serious wood guys selling their grinders after trying the pferd CSX / stihl 2 in 1 easy file I’ve bought one to try. It’s just over £30 so a bit more costly but the comments from guys that know their chit are that its a fabulous tool.
It isn’t much more costly than a round file and guide, roller guide and a flat file to be fair.
I got a second hand one of the right size for some of my chains on eBay for £26. Cheapest new I found was the pferd (blue handled version) on ebay but listed as stihl. They didn’t have the other size I need though annoyingly.