After buying several strimmers over the years, I eventually realised that a secondhand Stihl is 10 times better than anything else. They come up on eBay all the time. (Obviously don't go for one of the very heavy commercial ones!)
Alternatively, of the other makes, I quite liked a little Ryobi that was on offer at B&Q one time. Lightweight and handy, and very capable while it lasted. Refilling the line was a bit of a performance, though.