Best type of trimmer

We have a PR trimmer given to us and now we know why as it does not have an auto feed plus a few other problems. We mainly use it for trimming the grass where it is up against a fence and also for cutting the grass that overlaps onto the pathway.
Can any one suggest a good reliable trimmer that can do this and has an auto feed, but does not cost the earth?

 

I have had several strimmers, all had "auto-feed" but none of them worked well. I've now given up and feed the line by hand when needed.

 

Unfortunately due to disability need something to help with trimming lawns to make life a bit easier. Any other suggestions.